Which Galaxy S II is better? T-Mobile’s vs. AT&T’s

Customers on U.S. GSM networks have two similar Samsung Galaxy S II smartphones to choose from: one for AT&T(s t) and one for T-Mobile. While both are essentially the same phone, there are some subtle differences in both the internals and outside appearances. I have a review unit from both carriers, and while both are generally outstanding Google Android (s goog) handsets, customers deciding between the two should understand the key differences.

I’ve only just received the T-Mobile version over the weekend, while I’ve had the AT&T model for two weeks. So far, these are the differences I’ve spotted, outside of the actual dimensions of the handsets; you can see the size differences in the below image gallery.

What do these hardware and software differences mean in terms of real world use? So far, I don’t see much difference in the overall performance of these phones, even though they have different processors. Benchmark programs have yielded varying results, but what matters is how the phones work. They’re very comparable for browsing, navigating and running apps. The AT&T version actually feels slightly faster, but the variance is barely detectable, and most consumers wouldn’t likely see it. Besides, both run faster than most Android phones on the market today.

The wireless connectivity is a big variable, however. AT&T not only has a slower radio in its model, it has fewer coverage areas that support such speeds. My speed tests show the T-Mobile version is much faster where I live, and that’s only in a 21 Mbps area: 9 Mbps down on T-Mobile compared to 4 Mbps on AT&T. My podcast co-host Matt Miller tested the Galaxy S II in a 42 Mbps T-Mobile coverage area and found the phone to rival or exceed speeds provided by Verizon’s (s vz) LTE network.

Displays on the two phones use the same 800×480 resolution and Super AMOLED Plus technology. The main variance is the size, and to my eye, the AT&T display looks better. Because it’s slightly smaller, it has slightly more pixels per inch. And even when setting both displays at the same 50-percent brightness, the colors look better on the AT&T model: more vivid and less washed out. In my image gallery, you can determine which is better to you. Note in particular a picture I took in San Francisco. There appears to be less contrast on the T-Mobile version.

Both handsets are generally lasting a full day, so I don’t see much difference in the battery capabilities. I do like how you can swap microSD cards in the T-Mobile version without turning the phone off, although most people probably won’t care about that feature. Far more important to me though is the lack of Google Talk video support on T-Mobile’s Galaxy S II. The carrier opted to pull support in lieu of Qik’s video chat service, which is pre-installed. AT&T’s phone supports Google Talk video chat and my tests have proved it to work extremely well.

All in all, both phones are superb; the best Android devices I’ve used yet. But due to subtle differences, local coverage areas and your own personal preferences, one Galaxy S II might be better for you over the other. Bear in mind that there’s also a slight difference in the pricing: AT&T’s version is $199 with contract, while T-Mobile is initially selling its Galaxy S II for $30 more.