As posted in another thread, if i were verizon, my response to that ad would be this map..
However, the data most people look up while on a phone call (contacts, emails ect) is not an issue as the data is usually on the phone and doesn't need to be downloaded. You can check information on your phone all day long while on a call.
I just saw a new AT&T commercial where Luke is claiming the the AT&T downloading is faster than Verizon. But you never see where he's at other than inside. It's some secret area undisclosed because all the Iphone folks would converge on the spot and they'd soon be the same as New York and San Francisco, overloaded and threatening to limit in some way how customers use it. Fringe area for Verizon and strong signal for AT&T, it would be possible. Just tilt the conditions in your favor.