What i noticed on my short two days with verizon...
1. I had 5 bars it seemed like everywhere..wow
2. I work in a 500,000sqft building and i never get reception with AT&T in the middle of it, with verizon i had 2-3 bars all the time, i could not believe it!
3. Overall at the peak AT&T's speeds were faster, at the max with AT&T here i get about 4mb down with 1.3mb upload. However! This is usually always early in the morning or later in the evening. During the day it seems to slow down dramatically to a crawl sometimes, but on average during the day it will stay around 1.0 -1.5mb down, .75 up.
4. With Verizon i was VERY surprised with the speed of there 3g, it is much slower than AT&T but you will only notice this downloading apps it seems or maybe an HD video. There latency times were always around 120-150ms for me, while AT&T was anywhere from 145-300ms. This even when the latency times were roughly the same during parts of the day the AT&T just has some additional delay to it for some reason that the test don't pick up. Verizons speed were slower but were way more consistent, upload would peak around .90 at its best, but average i would say is .60. The download would stay steady all the time aright around 1.0-1.2mb.
5. Call quality, I never had an issue with calls dropping in my 7 or 8yrs with AT&T. I maybe dropped 5 calls over all these years. The big difference i noticed is that on the verizon iphone the sound had a lot more natural bass to it, and i never noticed it until then that the AT&T voice quality has this ice picking shrill sound to it, boost up the bass if possible on AT&T's side and they would be equal IMO.
I have been HUGE AT&T supporter over the years, but I do see what all the fuss is about with Verizon's network is now..