The Moto X's face is a similar size to the Galaxy S6 and Galaxy S6 edge, with Motorola's phone coming out just a hair shorter and wider.
The Moto X's thickness measurement is a little deceiving, as it has a rounded back and this spec only counts its thickest point. But Samsung's phones are still much thinner.
The Galaxy S6 is 4 percent lighter, and the GS6 edge is 8 percent lighter, than the 2014 Moto X.
The default Moto X has a plastic back (it feels a bit like faux metal), but you can also order natural wood or leather options. Samsung's phones have glass (Gorilla Glass 4) backs.
All three phones have aluminum frames, to complement those backsides. The Galaxy phones clearly have the higher-end builds here, and are really only rivaled in that respect by the latest iPhones and HTC One M9.
The Galaxy S6 will ship in four different colors (though US carriers are only offering the first two or three at launch).
Motorola lets you customize your own Moto X online, and, by our count, there are 540 total color combinations (after factoring in back, front and trim options).
The Moto X's display is 4 percent bigger.
Navigation buttons location
In many apps, though, that advantage is cancelled out by the fact that the Moto X has a persistent row of virtual navigation keys on its screen. Those do fade out, however, when Android's Immersive Mode kicks in (in places like photo, video and some reading apps).
The Samsung phones have a physical home button and capacitive back and recent apps keys sitting below their screen, so they'll never intrude on your available real estate.
This is a big advantage for the Galaxy S6 pair, as their ultra-sharp Quad HD screens are nothing short of spectacular. The Moto X's 1080p doesn't look bad at all, but you miss out on that eye candy that Samsung's phones give you.
All three phones use AMOLED panels, delivering rich colors and deep blacks.
Curved displays often come off as solutions in search of problems, but the Galaxy S6 edge has a simple use for it: make an already good-looking phone stand out even more.
While mostly cosmetic, the Galaxy S6 edge does give you the option of viewing notifications and launching apps from the curved bleed-off portions of its screen.
Samsung's moved from swipe-based to touch-based fingerprint sensors with the pair of Galaxy S6es. The Moto X doesn't have any biometric sensors.
You can use those fingerprint sensors with Samsung Pay, the company's aggressive answer to Apple Pay. Unlike Apple's method, though, Samsung's works with swipe-based credit card machines, making it nearly universally accepted from the get-go.
The Moto X is compatible with Google Wallet, which has been around for years and has yet to really take off, but is still accepted at many of the places where Apple Pay is. Google Wallet doesn't, however, use fingerprint authentication.
The Galaxy phones are absurdly fast, with their octa-core Samsung Exynos processors. The Moto X is far from a slow phone, but its processor is a generation behind the latest Snapdragon devices, like the HTC One M9 and LG G Flex 2.
RAM is another advantage for the GS6 and edge.
You also get double the storage at the entry level, and an extra tier to choose from, with the Galaxy S6 pair.
None of the three let you complement that internal storage with a microSD card.
The Galaxy S6 phones' batteries hold a bit more juice, but you'll want to keep your eyes peeled for our Galaxy S6 and edge reviews before jumping to conclusions about battery life.
All three batteries are sealed shut.
The Moto X uses Qualcomm's Quick Charge 2.0 tech to juice up your phone quickly from a nearly-dead battery. Samsung's phone is likely using different tech, but has a similar feature.
The Galaxy S6 and GS6 edge have wireless charging capabilities built-in. The Moto X doesn't.
Camera megapixels (rear)
The Galaxy S6 handsets have higher-resolution rear cameras, and (again, stay tuned for our review for confirmation) will most likely have superior all-around rear cameras.
Camera megapixels (front)
The Samsung phones also have higher pixel counts in their front shooters.
The GS6 pair's rear cameras also have wider apertures.
Camera quick launch
The Moto X has a nifty gesture shortcut that lets you launch its camera by twisting your hand a couple of times. Samsung's quick launch method might be even easier, as a double-tap of the home button launches the camera on the Galaxy S6 or GS6 edge (spoiler: it launches ridiculously fast).
Gear VR compatibility
The Moto X should work just fine with Google Cardboard kits, but the GS6 pair play nicely with the new version of the Oculus-powered Samsung Gear VR, the best virtual reality headset you can buy today.
Heart rate monitor
The GS6 pair, like last year's Galaxy S5, each have a heart rate monitor.
Both phones have Android Lollipop at their core. Technically there are some light Motorola customizations on the Moto X (light Moto Display, which pulses notifications on an otherwise dimmed screen), but it's otherwise a stock Android experience. The Galaxy S6 has a much subtler layer of Samsung's TouchWiz UI this year (with less bloat), but it still has its own identity and won't be mistaken for "vanilla" Android.
We're comparing Samsung's early 2015 flagship to Motorola's late 2014 one. Going off of the established pattern, we could be about five months away from a third-generation Moto X.
Starting price (full retail)
Technically the Moto X still starts at US$500 full retail, but you should be able to find some deals on it for cheaper than that.
Off-contract pricing for Samsung's phones is varying quite a bit among the US carriers. These figures seem to be pretty good median ranges based on what we've seen from T-Mobile, Verizon, Sprint and AT&T.;
Starting price (on-contract)
These are much firmer among the carriers, as $200 and $300 seem to be the consensus on-contract starting prices for the Galaxy S6 and Galaxy S6, respectively.