The thing is IIRC AT&T, in the Bay Area at least, always seems to win the Speed Tests against Verizon [1]. However as a long time user of AT&T on the iPhone in SF the issue was never speed it was the ability to actually use the network which was problematic. I couldn't get phone calls in my apartment in Poterero Hill and still get dropped calls on my cell in our house in Berkeley (we were eventually forced to get a land line). I never had these problems with Verizon (which is why my wife and I are switching once the new iPhone's come out). Point being I find these kinds of comparisons meaningless unless their coverage gets better.

[1] http://www.pcmag.com/article2/0,2817,2364263,00.asp