Giant, bold mega-phones are the new smartphone trend, and the impressive Samsung Galaxy S III ($279.99 with contract) is T-Mobile's first offering. With its 4.8-inch HD screen and state-of-the-art sharing and media features, the Galaxy S III makes a great window onto T-Mobile's fast 4G Internet. Its overall performance and quality make the Galaxy S III our new Editors' Choice for touch-screen smartphones on T-Mobile.

Editors' Note: The Samsung Galaxy S III models on all four major carriers are extremely similar, so we're sharing a lot of material between our various reviews. That said, we're testing each device separately, so read the review for your carrier of choice.

Physical Design
All of the new Galaxy S III models look the same, except for the carrier logo on the back panel. Each is available in dark blue or white (AT&T also has a red option coming this summer), and they're some of the biggest phones we've ever handled. At 5.4 by 2.8 by 0.34 inches (HWD) and 4.7 ounces, the GS3 is larger than the HTC One S ($199, 4.5 stars), although it's still noticeably smaller and lighter than the Samsung Galaxy Note phone/tablet hybrid ($299, 3 stars).  That said, this is not a phone for folks with small hands.

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I'm not a fan of huge phones. But I've given up on panning them because every time I suggest these handsets are too big, I get pummeled by comments from people who adore them. Huge phones are the thing. I accept it.

The GS3's all-plastic body feels a little less high-end than the anodized gray aluminum of the HTC One S, but the phone is solidly built, and light despite its size. The front of the phone is dominated by the 4.8-inch, 1280-by-720-pixel Super AMOLED HD screen. Yes, it's PenTile, which can sometimes look slightly pixelated. But, no, you probably won't notice. Below the screen, there's a physical Home button, as well as light-up Back and Multitasking buttons that start out invisible, so you have to memorize where they are or change a setting to keep them illuminated. The 8-megapixel camera is on the back panel, which, thanks to its reflective finish (on the blue model), doubles as a pocket mirror. 

The default Automatic Brightness setting makes the screen too dim. Kill it and pump up the brightness and it's fine, even outdoors. 

Unlike the competing HTC One S, the S III has a removable 2100mAh battery. Taking off the back cover also reveals the microSD card slot, which supports cards up to 64GB.

Call Quality and Internet
If you're interested in talking on your smartphone, buy the Galaxy S III. Its advanced call quality features make a real difference. Default call quality is good. Volume is on the high end of average, with no distortion from loud inputs, and the speakerphone is loud enough to use outdoors. The microphone does a good job of cancelling background noise. Bluetooth headsets work fine with Samsung's "S-Voice" voice dialing system, and the phone supports T-Mobile's seamless Wi-Fi calling system.

But as with so many things here, call quality gets richer if you burrow down into the GS3's settings screens. A Volume Boost button throws the phone into a super-loud, quasi-speakerphone mode for noisy areas, but that's just the start. There's also an option to set custom call EQ: The phone plays you a sequence of quiet high and low tones and you tell it which ones you can hear, and then it EQ's calls accordingly. This is pretty radical stuff. I prefer my calls sharp, with more high-end, for instance, and the GS3 offers that. This all makes the GS3 the best voice phone on T-Mobile.

For data, the GS3 hits T-Mobile's HSPA+ 42 network, which can sometimes match AT&T's and Verizon's LTE on download speeds. It hits global HSPA+ and Wi-Fi on both the 2.4GHz and 5GHz bands, and Bluetooth 4.0 and NFC are also on board. T-Mobile still blocks Google Wallet, but Samsung found its own uses for NFC, which I'll get to below.

Battery life is a major strength here. We got 10 hours, 47 minutes of talk time, which is impressive, and, since the battery is removable, you can also carry a spare for extra juice, something you can't do with the HTC One S.

Software and Performance
The Galaxy S III runs Android 4.0 "Ice Cream Sandwich" with a whole lot of exclusive Samsung extensions. Performance was excellent in my tests. The Qualcomm S4 chip running at 1.5GHz is the fastest one we've seen in smartphones so far, and it's able to take on any app challenge you throw at it, including games on the HD screen. Our benchmark tests proved this, although they were within the margin of error when compared with the One S. Both phones are very fast.

Exclusive new features include S-Beam, the ability to transfer files by tapping two phones together and using a combination of NFC and Wi-Fi Direct; S-Voice, Samsung's answer to Apple's Siri; and TecTiles, NFC-enabled accessory tags that can change the settings on your phone. You also get lots of sharing and tagging options in the camera, such as automatically tagging your friends' faces, and the ability for multiple GS3s within a few feet of each other to automatically share all of their photos.

Many of these features work well, but they're almost all buried. The interface is something of a scavenger hunt. Take Smart Stay, a neat new feature which detects your face and keeps the screen from going black while you're looking at it. I love it! But it's not on by default, and the only way to turn it on is by going to the Display area under Settings. S-Beam is similarly buried, under the Wireless menu.