When we compared the Galaxy S5 to Apple's iPhone 5s, we saw a huge size difference. That isn't the case here. These are two big phones, with equally big (and beautiful) ~5-in screens. The HTC One M8 is 3 percent longer, 3 percent narrower, and 16 percent thicker than the GS5. But those are pretty minor discrepancies. Don't expect a dramatic difference when you first see each phone.
Cosmetically, and in terms of build quality, well, that's a different story. The One M8 is one of the most stunning smartphones ever made, with its aluminum unibody design. The gun metal color option for the One (pictured in this article) is particularly striking. Its subtle brushed finish looks unlike anything we've seen on another smartphone. HTC takes design seriously, and it shows.
The Galaxy S5's build, on the other hand, is more of an – ahem – acquired taste. Its backing is made of fake leather ... with dimples. Its look has been compared more than once to a Band-Aid. And though the band that runs around the edge of the GS5 has a metallic look, well, it turns out it's made of plastic too.
If you want a phone with a premium construction, high-end design, and acute attention to detail, then you can pretty much stop right now. The One M8 stands next to the iPhone 5s as the current prototypes for making an elegantly-designed smartphone. As for the Galaxy S5, I don't think its design is quite as offensive as some reviewers think. But you also can't deny that this is very much a plastic phone. Samsung seems content to make mobile devices that, from a distance, look like they might have a high-end design. Enjoy the illusion if you want, but look closer, and you'll find that you're living in plasticville.
The Galaxy S5's faux leather finish does, however, have a couple of perks. First, it helps to make the GS5 9 percent lighter than the One M8. But, more importantly, its slightly soft-touch pleather finish makes it more comfortable to hold. It's a pretty big phone, so a material with some give to it is going to feel a little cozier in hand than one made of a rock-solid aluminum.
One of the M8's most obvious physical touches is its front-facing speakers. Flanking its screen, above and below, are two speaker grilles – bigger than you'll see on just about any other phone. And the resulting audio from HTC's "BoomSound" speakers is easily the best I've heard out of any handset. That isn't necessarily saying much, as most phone speakers sound like garbage. But I do find it almost shocking how loud and full the One's speaker audio is. And if you've used the original HTC One (M7), which already had impressive audio, the M8's speakers sound noticeably better.
Screen size is very close, with the One M8 sporting a 5-in screen and the Galaxy S5 cranking that up to 5.1 inches. That translates to the One giving you 96 percent as much display real estate as the GS5.
If we left the screen size comparison at that, then I'd say the difference is negligible. But there is one more big item here. The One M8 uses virtual onscreen navigation keys, while the Galaxy S5 uses (below-screen) physical and capacitive keys. That means the GS5 will always give you 100 percent of its display area, while the One M8 will have a bottom row set aside for virtual home, back, and recent apps buttons.
The exception is when Android's Immersive Mode kicks in. It fades out those navigation buttons in places like your image gallery, videos, and a few other apps (you can just swipe or tap on the screen to bring the buttons back). Those are probably the most important places to use the One's full 5-in screen, so you could argue that it's doing just fine in that department. But also know that any Android apps you use that don't support Immersive Mode (most of them) will leave you with a little less than its full 5-in screen area.
There isn't much to say about display quality, except that the screens on the One M8 and the GS5 both look terrific. They have extremely sharp 1080p displays, with vivid and accurate-looking colors. I wouldn't recommend basing your decision on display quality, one way or the other. They both ace that class.
The Galaxy S5's killer feature is its IP67 water resistance. That means it can soak in 1 meter (3.3 ft) of water for 30 minutes without any problems (just make sure its battery and charging covers are sealed shut). If you've ever fantasized about checking your phone in the bath, shower, or shallow end of a pool, then the GS5 might be just what you're looking for. Ditto for anyone who's prone to dropping his phone in the sink or toilet. The HTC One doesn't have any water resistance on board.
The GS5 also has a heart rate monitor. It lives on the phone's backside, just below its rear camera, and is tied to Samsung's S Health app. The Galaxy S5 is the first phone to include a dedicated pulse sensor, but there are also Android and iOS apps that let you check your pulse – using the camera lens and flash. If given the choice, I'd still go with the GS5's dedicated sensor, but I also wouldn't buy the GS5 just to get a dedicated heart rate sensor.
Samsung also included a fingerprint scanner in the Galaxy S5. Similar to the iPhone 5s, the GS5's home button doubles as a biometric sensor: just swipe your finger across it to unlock your otherwise passcode-protected phone. In my experience, the sensor is very accurate. It almost always recognizes my swipes and it won't authorize any non-programmed fingerprints. But since you do have to swipe your finger, instead of just resting it on the home button (like on the iPhone 5s), the GS5's fingerprint sensor is a little slower and less convenient than Apple's Touch ID.
The biggest perk that the GS5's fingerprint sensor has is its integration with third-party apps. You can use your print to login to PayPal (and authorize PayPal transactions), as well as login to the LastPass password storage app. We'll probably see more apps incorporating the GS5's scanner as the year goes on.
HTC's 2013 phablet, the One Max, had a fingerprint scanner on its back (which I didn't like very much), but the company passed on putting any biometric sensors in the One M8.
HTC did throw some new sensors into the One M8, though they aren't quite as in-your-face as the heart and fingerprint tech baked into the GS5. HTC's Motion Launch is a set of motion sensor-based shortcuts that let you jump to different areas of your phone a little quicker than you'd otherwise be able to.
One example: when holding your One M8 in portrait mode with the screen off, you can just swipe up on the screen to jump straight to your home screen. Likewise, you can swipe to the right on the turned-off screen to jump straight to BlinkFeed (HTC's news feed home screen widget), or left to go to your other widgets. You can also double-tap on your sleeping One's screen to quickly check your lock screen.
Maybe the most useful Motion Launch shortcut, though, is the one that lets you fire up the One's camera just by holding the phone in landscape mode and pressing one of its volume buttons. The Galaxy S5's camera is notoriously slow to launch, and HTC's shortcut gives it even more of an advantage there.
Both phones have good cameras – as does basically every high-end smartphone from the last year or two. The GS5's has a much higher resolution (16 MP to the One's 4 MP), but the One's camera has a few perks of its own.
The biggest is the One's low-light capabilities. Say what you will about the low resolution in the One's UltraPixel camera (and you will have a few select words for it if you zoom in close or make tiny crops from shots you've taken), but it performs better in the crappiest of lighting conditions than just about any other phone I've used. Though the One's low-lit shots can look a little muddy, they do appear brighter and more saturated than other phones' poorly-lit shots do – including the Galaxy S5's.
The One M8 also has a dual-LED flash that can help to make its flash shots look more balanced and saturated. I tested both phones' cameras with flashes on, and the One's shots did look a bit more colorful and even – with less of that washed-out, center-focused, flash-blasted look that we're used to seeing from flash photography.
The One also has a second camera on its backside, devoted to sensing depth. This opens the door to a few kinda cool, kinda gimmicky features that play with depth.
My favorite is UFocus, which simulates the kinds of blurred background shots that you'd get from a much better camera. The One M8 uses its depth sensor to blur and focus different areas of any given shot. You can choose one point of focus, save it, choose another, and save it (and so on).
UFocus doesn't, however, always work perfectly. Sometimes it will think straggly pieces of the background are connected to the foreground, creating odd effects like a sliver of a background streetlamp extending from a person's head (like some kind of bad 80s hairdo). But when UFocus works well – which is, I'd say, about 60-70 percent of the time – it's a pretty brilliant feature to have on your phone. It's the closest I've seen any phone get to replicating the bokeh shots you'd get from a wide-aperture DSLR.
The Galaxy S5 also has a feature that lets you blur backgrounds and shift points of focus, but I don't think it's nearly as good. The GS5 doesn't have any depth-sensing hardware, so the phone uses software algorithms to try to create those bokeh shots. It works well enough, but there are a few catches. First, you have to be within 1.5 ft (45.7 cm) of your subject. Step farther back, and it won't even let you use the feature. The subject's background also has to be at least 3x as far away from it as it is from you.
Is this still a feature worth having on the GS5? You bet. But just know that it's a) much more limited than the One's UFocus, and b) much less amazing than Samsung's TV commercials are going to let on.
Both the GS5 and One M8 have terrific battery life. We put both phones through a test where we stream video with brightness set at 75 percent. The GS5 lasted 9 hours, 27 minutes. The One M8 lasted 9 hours, 20 minutes. Both are terrific results. You'll want to take these kinds of tests with a few grains of salt (there are lots of variables that can affect battery life, depending on your wireless signal and other settings), but I can vouch for both of these handsets' uptimes. Neither gives you anything to worry about.
Both phones also have a terrific new feature that can really extend your battery life in a pinch. Samsung first unveiled the GS5's Ultra Power Saving Mode in February. Switch the feature on, and it will shift its screen to black & white and severely limit background processes. You're left with email, text messaging, a web browser, and a few other options. Samsung says that Ultra Power Saving Mode will give you an extra 24 hours of battery life from just 10 percent juice. In the testing I did with this feature, I'd say that sounds about right.
The One M8 also has a version of the same battery-extending feature. Announced a month after Samsung's version, HTC's Extreme Power Saving Mode is basically the same deal, with the added bonus that you can set HTC's to kick in automatically when your battery dips to a certain level. Extreme Power Saving Mode hasn't yet rolled out to the Verizon One M8 I've been using, so I haven't yet put it through the paces. But based on what I've heard from others, it should work as advertised.
I've used the Galaxy S5 and HTC One M8 since they launched, and I think they're both excellent smartphones. But is one better than the other? Well, one person's "best" can be another's turd, so we don't claim to have a one-size-fits-all answer. But if I had to choose only one of these phones to use for the next two years, I think I'd just barely go with the HTC One. That stunning, premium design is hard to turn down. I also think Sense is a more elegant software UI than the GS5's TouchWiz. Some of the One's depth sensor stuff is gimmicky, but UFocus can often make for some killer blurred-background shots.
But I could almost as easily pick the Galaxy S5. Sure, its Band-Aidy pleather finish is pretty chintzy. I also think TouchWiz is jam-packed with too many features that work better in commercials than they do in actual experience. But, on the other hand, the GS5 gives you a bigger display than the One M8 (with even more available screen area) and is lighter and more comfortable in hand. Its fingerprint scanner adds some extra security and convenience, its camera takes much higher-resolution shots, and its water resistance lets you use your phone in places you've never used a phone before.
Though we don't have a universal winner to stamp onto this comparison, we hope this nudges you into the direction that works better for you. If you're still stumped, then you can hit up our individual reviews of the Galaxy S5 and HTC One M8. And if you're interested in jumping to the Apple side of the fence, you can read Gizmag's comparison of the Galaxy S5 to the iPhone 5s.