You probably aren't going to find two high-end smartphones as different as these two. Though we're only weeks away from a new iPhone, why not take the iPhone 5s' last moments in the spotlight to see how it compares to the LG G3?

Unless you're talking about qualities that every smartphone has, there really isn't a lot of overlap between these two. One is a huge phablet with skimpy bezels and more pixels than an HDTV. The other has the best fingerprint sensor that you'll find in any smartphone, along with a screen size that's a throwback to the smaller phones of yesteryear. We could write a book on the ways that these two differ, but, since you probably have better things to do during the next few months, let's cut to the chase and zero in on a few key differences.

The most obvious is size. Pick up the smaller iPhone, and it slides right into the meat of your palm. While gripping it, I can easily wrap my fingers around its sides – with room to spare. It's a breeze to use with one hand, and it practically disappears in your pocket.

Pick up the G3, on the other hand, and you feel something that's a lot more substantial. If you stash it in your front pocket, you'll know that it's there. It's also more of a two-handed device: one paw to hold it with, another to use for swiping and tapping its spacious display.

Specifically, the G3 is 18 percent longer and 27 percent wider than the iPhone. Apple's handset is also 15 percent thinner. The iPhone is an incredibly light phone: 25 percent lighter than the G3. Though to LG's credit, the G3 is relatively light for its size.

The build quality prize goes to Apple. The iPhone 5s has an aluminum unibody construction, complete with chamfered edges and sapphire-covered home button. As for the G3, well, it's made of plastic. It does, however, have a metallic film sprayed on top, giving it a somewhat higher-end aesthetic that it would otherwise have.

In hand, I can feel the difference. When I grip the iPhone, it's clear that I'm touching metal. You can immediately tell that Apple's designers didn't take any shortcuts. The G3 doesn't exactly feel chintzy – its faux metal finish helps it to look somewhat high-end – but there's also no doubt that you're dealing with plastic. Try as LG might, it's hard to hide that cheaper build quality.

But that doesn't mean that the G3's design doesn't have a lot going for it. The highlight is the front of the phone, which is almost entirely screen. The bezels above and below its display are small, and the side bezels are practically non-existent. LG's flagship has one of the best combinations yet of screen size to phone size.

Speaking of screen size, that's another huge difference between these two. The G3's 5.5-in display is a whopping 89 percent bigger than the iPhone's 4-in screen. Or, put another way, the iPhone only gives you 53 percent as much display real estate. No matter how you slice it, that's a huge discrepancy – and one of the biggest reasons to choose the G3.

The G3 also has a much sharper screen, but, to me, this difference is much greater on paper than it is in experience. Though the G3's Quad HD screen packs in 65 percent more pixels per inch (PPI), the iPhone's Retina Display still looks plenty sharp.

If you subscribe to the "sharper is always better" mantra, then the G3 is the clear winner. But its screen resolution is bordering on (if not crossing past the point of) overkill. I can just barely notice a difference between its display and the 1080p displays that we've seen on recent Android flagships. It is noticeably crisper than the iPhone's screen, but I'd describe this as "insanely sharp" vs. "very sharp." Unless you're obsessed with pixel counts, I wouldn't recommend basing your decision on this alone.

The G3's pixel-dense display also creates some compromises in other areas. In most modern high-end phones, performance is way past the point of concern – to the degree that we often don't even mention it when reviewing handsets. But, surprisingly, the G3's UI has a noticeable amount of lag – at least out-of-the-box. Since the phone has one of the fastest processors around (the Qualcomm Snapdragon 801), I suspect this has something to do with its GPU pushing those 3.6+ million pixels.

There is, fortunately, an easy fix for the G3's lag. Once you change the phone's runtime from Dalvik to Android runtime (ART), the lag issue pretty much fades away. If that sounds like gibberish to you, have no fear: it's an easy change, and doesn't require any advanced technical know-how. You can hit up our full G3 review for instructions on making this tweak.

The iPhone's performance, on the other hand, is buttery-smooth from top to bottom – no tweaks necessary. It has as much zip as I could ask for from any 2013-14 smartphone.

Battery life isn't a killer feature of either phone, but they're both in fairly good shape in that department. In our standard test, where we stream video over Wi-Fi (with brightness set at 75 percent), the iPhone lasted 6 hours and 15 minutes. The G3 lasted about five minutes longer. With typical use, I'd say both are easily all-day devices, but rivals like the Galaxy S5 and HTC One (M8) did score much higher than either of these.

Both phones' cameras snap photos quickly. The time it takes to go from sleeping phone to snapping a picture is an often overlooked feature (I found that the Galaxy S5's camera, for example, takes too long to fire up). But both the iPhone and G3 have snappy cameras. In both cases, I can go from sleeping phone to hearing the click of the shutter in 3 to 3.5 seconds.

As for the quality of the shots, well, both are very good choices. I would, however, give the advantage to the G3. It takes photos in a higher resolution (13 MP to the iPhone's 8 MP) and also uses a laser to help with autofocusing. Tap the part of the G3's screen that you want to be in focus, a laser beam fires to measure the distance between phone and subject, and the G3 automatically snaps the shot. On your end, though, it's as quick and simple as tap and snap.

The iPhone 5s' killer feature is its Touch ID fingerprint sensor, which, despite some competition from Samsung, is still easily the best in the business. After programming your fingerprint, you'll be able to unlock your (otherwise passcode-protected) iPhone simply by resting your finger on the home button for a brief moment (usually less than a second). You can also use it to authorize iTunes purchases and, with the upcoming iOS 8 update, third-party apps will even be able to integrate with the sensor. The G3 has no fingerprint sensor.

Like most recent flagships from Samsung, HTC and LG, the G3 has an infrared (IR) blaster. This lets you use your phone as a universal remote control for things like your TV or cable/satellite box. The iPhone doesn't have an IR blaster.

The iPhone 5s and LG G3 are both terrific high-end handsets. If you're looking for a beast of a phone with a huge screen, and don't mind tweaking a setting to get its performance up to speed, then the G3 might be what you're looking for. The iPhone, though, has a more premium aesthetic, with greater portability, smoother performance out-of-the-box and that terrific fingerprint sensor.

With the iPhone 6 looming on the horizon, though, this isn't a great time to buy the iPhone 5s. Actually scratch that: this is a terrible time to buy the iPhone 5s ... at least at full price. The rumor mill is pointing to two new models: a 4.7-in iPhone in September and a 5.5-in Apple phablet (the same screen size as the G3) that may launch a bit later. The G3 is an outstanding phone, but if screen size is the only thing pushing you in its direction, then you might want to consider waiting to see exactly what Apple has up its sleeve.

Though we hit the biggest differences between these two, there's more to the story. For a deeper dive on each of these handsets, you can check out Gizmag's full reviews of the iPhone 5s and LG G3.

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