Personally, I would never ever buy 3G iPads. I don't need GPS. My Phone has it.
With LTE just around the corner, I am not investing money on 3G iPads. And verizon 3G is just too slow. AT&T 3G is very good, but not reliable all the times.
Best option is clear iSpot 4G. Unlimited data for 25 dollars a month with speed 6Mbps.