I do believe, in a very narrow way, iPhone is "better"... however, as spacecasespiff is suggesting: "Better how?" My son is on at&t w/iPhone and is not happy with the service. I have an "old" G1 and am very satisfied with the service TMo provides. A close friend has an iPhone and it's unlocked so he can use it on TMo and would never use at&t. Then there's the question of the iPhone's reception. My son (and his GF) both have reception problems with their iPhones sometimes even in major metropolitan areas. For me these two, related, issues more than off-set any advantage the iPhone may have. The last time we were in Europe I meant to do a side by side roaming comparison. Next time.
Also, have a look at this: http://bits.blogs.nytimes.com/2010/07/12/consumer-reports-says-iphone-4-has-design-flaw/?src=me&ref=general