If I were to get an iPad with 4G LTE, I’d get the one on Verizon network. That’s because Verizon includes Mobile Hot Spot into the plan.
From Verizon Wireless iPad page:
Mobile Hot Spot Support For The New iPad.
Verizon is the only carrier in the U.S. that allows the new iPad Wi-Fi + 4G to act as a personal mobile hotspot. This means you can share your Verizon 4G LTE network with up to 5 Wi-Fi enabled devices (such as a computer, gaming device or camera). And the best part? This personal hotspot is available at no extra charge and simply uses your data allowance.
Dear AT&T, I am not buying one for your 4G LTE network.