I have had every AT&T iPhone model from original through 4. Switched to VZ because I sold the 4 on gazelle for $410 plus 15% bonus code (switching costs a wash). Live in the NYC metro area. AT&T was perfect exactly where I lived but had the usual complaints while travelling around. I travel upstate often where VZ has a big coverage advantage.
Here's the quick summary: Consistency. The VZ iPhone is consistently reliable. Not a single dropped call. Yes data is "technically" slower on speed tests (i've seen over 2mb down on VZ in places I saw 3 on AT&T but really, no real world difference). Even on 1x data still works where as on edge hardly at all. The phone works deep into buildings where AT&T would be questionable. I'm very happy.
Here's the quick summary: Consistency. The VZ iPhone is consistently reliable. Not a single dropped call. Yes data is "technically" slower on speed tests (i've seen over 2mb down on VZ in places I saw 3 on AT&T but really, no real world difference). Even on 1x data still works where as on edge hardly at all. The phone works deep into buildings where AT&T would be questionable. I'm very happy.