I guess that really depends on where you're using your iPhone. Check out Daring Fireball's piece: http://daringfireball.net/2011/02/verizon_iphone_4

Gruber's results:

AT&T: Download 1.87 Mbps, Upload 1.18 Mbps and Ping 284 ms

Verizon: Download 1.28Mbps, Upload .48 Mbps, and Pring 281 ms

"These tests were conducted in my home office in Philadelphia. I lacked the foresight to conduct them before leaving San Francisco. For downloading, AT&T is a little faster. For uploading, it’s a bit more than twice as fast. And latency is about equal."

AT&T service in SF is a joke at best. I switched to a MyTouch 4G this last saturday after having the iphone since day-1 launch.

I have gone through 9 iPhone handsets for various reasons...

I cannot tell you how happy I am to be off that phone. It sucks compared to the MT4G and the service I get now is amazingly fast.

AT&T should be sued for the dismal everything they offer.