I was really hoping T-Mobile would be different at my house, but in practice it was about the same as AT&T. Every time I checked both phones together, they showed the same: one bar of LTE, or maybe two bars of 4G, and when I averaged 10 of those one- to two-bar LTE tests on each phone, I got 0.9Mbps down for T-Mobile and 1.2Mbps for AT&T.
At my office in San Francisco, also marked as Excellent on T-Mobile's map, I was typically seeing two to three bars of LTE, and speeds averaging a respectable 4.7Mbps down after 10 tests. Again, this is about the same as I was seeing on my AT&T iPhone.
But when I managed to find a strong LTE signal from T-Mobile around town, its speeds were impressive. My best test in California was at the Oakland airport, where 4 bars of LTE got me 23Mbps down and 9.25Mbps up. At my brother's house in the Chicago suburbs, T-Mobile beat AT&T, even though AT&T had an extra bar when I tested.
So for me, the network performance is pretty much a wash, with a slight edge to AT&T. T-Mobile does come with some extra perks like free music streaming: If you use Pandora, Spotify, Rhapsody, iHeartRadio, iTunes Radio, Milk Music, Slacker Radio, or Beatport SFX, all the music that you stream over the cellular connection won't count against your data plan.
While it's true that T-Mobile ditched overage charges, you still have a high-speed data bucket, and when that's gone, you can keep using data at a slower speed without paying more. But now you'll be able to stream music without it hitting that high-speed data bucket, and if your high-speed data is gone for the month, you can still stream music at high speeds.
If your current carrier dings you for overage or throttles your speeds, or you're just afraid to stream music over cellular because you're worried that'll happen, this could be huge. Streaming an hour of Spotify used 51.6MB, an hour of iHeartRadio was 60.5MB, and an hour of Pandora was only 35.4MB. But a couple hours a day, five or six days a week, and that adds up fast.
Will I switch because of this test drive? Probably not. I might ask AT&T for a MicroCell to improve reception at my house, but it works fine at work and around town. T-Mobile's free music streaming is a great perk if you use it, and I do love to stream music, but I use Rdio, which isn't currently in T-Mobile's program. (The carrier is taking feedback from users on which services, if any, to add.) And I'm not worried about using too much data when streaming Rdio, either, since I still have the "unlimited" data plan that I got in 2008 with my iPhone 3G. (AT&T does throttle my speeds after 3GB, but most months I only use around 2GB.)
Sign up for CIO Asia eNewsletters.