As you can see, we're comparing a standard-sized smartphone (by today's standards) to a supersized one. The Samsung Galaxy Note 4 is 6 percent taller and 13 percent wider than the HTC One M9.
Neither handset is going to win any prizes for thinness, but the Note 4 does come out around 12 percent thinner. Though you'll want to take into account the fact that One has a more rounded backside (and its measurement only counts its thickest point).
Likewise, neither is going to give the iPhone 6 and Galaxy S6 a run for their money in the weight department, but neither should feel unusually heavy either. The larger Note 4 comes out at 12 percent heavier.
The entire HTC One legacy, starting with 2013's One M7, has the same killer feature: that smooth, stunning, aluminum unibody build. It's changed a little bit since then, but HTC is clearly iterating on the same basic design language.
Though the Note 4's build doesn't have the same high-end aesthetic, its aluminum frame helps out in that department, making it feel more premium than older (all plastic) Galaxy flagships did.
HTC and Samsung each give you four color options to choose from.
Again, we're clearly looking at two different categories of devices, as the Note's screen is 30 percent bigger.
Navigation buttons location
The M9 uses up some of that real estate on a row of navigation buttons, though Android's Immersive Mode will fade those out (giving you access to the full display) in certain apps.
It was a little surprising that HTC stuck with 1080p resolution for the One M9. Make no mistake: that's still very sharp. But it doesn't have quite the same eye candy effect that Quad HD displays, like the Note 4's, give you.
... though it is worth noting that, due to the size difference, the Note's Quad HD screen is only about 17 percent sharper than the One's 1080p display. That difference will be more pronounced on smaller Quad HD displays like those on the LG G3 and Samsung Galaxy S6.
No changes from previous years here, as HTC sticks with an IPS panel, while the Note uses Super AMOLED display tech.
The S Pen goes hand-in-hand with the Galaxy Note line, both with its note-taking features and by simply giving you a more precise pointer than your stubby fingers could ever be.
The One M9 has a leg up here, and should have a performance advantage – with Qualcomm's newer (64-bit, carrying two quad core CPUs) Snapdragon 810 chip, which also includes a (slightly faster) Adreno 430 GPU.
As always, though, performance is best measured by experience, so stay tuned for our One M9 review.
The M9 is the first HTC One flagship with 3 GB of RAM.
HTC is making your storage decision very easy, as the M9 is only shipping in a 32 GB tier.
Though Samsung's new GS6 flagships lose their microSD cards, both of these handsets let you pop in an SD to complement your internal storage.
The Note 4 has good battery life, as did last year's HTC One M8 (and HTC is promising longer uptimes with the M9). Here too, you'll want to check back for our M9 review for more on this.
Like many plastic phones, you can peel the battery cover off of the back of the Note 4 and swap out its battery. Like most metal phones, the One M9's battery is sealed shut.
Both handsets use Qualcomm's Quick Charge 2.0 tech to juice your phone up to a respectable state fairly quickly (though you'll only see this boost when you're starting from a nearly spent battery).
Ultra/Extreme Power Saving Mode
HTC and Samsung both offer special power saving modes that each do basically the same thing: give you simplified home screens and severely limit available apps, so you can stretch a few percentage points of battery into hours (if not a day or so) of extra uptime.
Camera megapixels (rear)
So much for HTC's "it's about pixel size, not pixel count" argument. This year it's all about pixel count, as the M9's rear camera jumps from 4 MP (found in the first two One flagships) to 20 MP.
Camera megapixels (front)
The UltraPixel camera does live on, however, in the One M9's front-facing camera.
The Note 4's rear camera has a slightly wider aperture than the M9's.
Dual LED flash
Samsung didn't include this in the Note 4, but the M9 (like several other high-profile flagships) has a dual LED flash. This can help to even out and saturate the appearance of flash shots.
Included accidental damage warranty
HTC's new Uh Oh program includes accidental damage coverage from one year of your One M9 purchase. It's only a one-time deal, but it lets you replace your M9 in case of water damage, cracked screen or even switching carriers. If you never take HTC up on that replacement, you'll get US$100 off of next year's One (a year after your purchase of the M9).
Samsung improved on this with the Galaxy S6 (going from swipe-based to touch-based), but the Note 4 does have a fingerprint scanner – something HTC didn't bother with in its latest flagship.
Heart rate sensor
The Note 4 also has a heart rate monitor on its backside, just below its rear camera.
The M9 will play nicely with Google Cardboard VR kits, but they aren't nearly as consumer-ready as the Gear VR is (though technically Samsung and Oculus don't yet consider the Gear to be a full-blown consumer product either).
Either handset lets you change channels on your TV, with built-in infrared capabilities.
It's been over five months since the Galaxy Note 4 launched, while the One M9 will start rolling out to US carriers beginning on April 10 (though we don't yet know exactly when each carrier's version will start shipping).
Starting price (full retail)
Carriers will have their own pricing for the One M9, though if years past are any indication, it would run around $650 off-contract.
Starting price (on-contract)
In previous years, One flagships started at $200 on-contract, and we wouldn't be shocked to see the same with the M9, once carriers announce the phone on their respective networks.
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