Just read t-mobile vs. verizon and I have to agree with the conclusion (vzw beats tmo every day of the week). I'm a tmo customer since I get the plan as part of my compensation package. So I ran the same tests on my phone and the best I could do was 190 kbit/sec with the 1MB test (I couldn't figure out how to do a screen capture).
I really like the sp5 (despite the lack of a2dp support, more on that later) and the new push email support rocks. Whenever my phone buzzes at work I know that I need to hit send/receive in Outlook. But I'm definately tempted to make a switch to vzw because of the faster data access (Sprint is just as fast, but do you really want to deal with that company?).