I honestly don't understand the hype with verizon mifi. As a sprint mifi user its great for a device without a built in device.. but a whole other device to carry and care for?? Seriously?? I could understand if in your area AT&T 3G service sucks but why not try that first then complain about AT&T sucks or you hate AT&T and whatever else you feel to complain about as if other cell companies don't have the same exact issue, which they do.
I say try the 3G on your iPad. If it works good, then AT&T is good for you. And just so you know, verizon data pricing structure is worse than AT&T data wise..
I personally like AT&T service in my area. It's quick and yet to fail me. I have tmobile on my iPhone and that's great, though edge is slow.. But I've been wihh them for 5 years for personal use. AT&T and sprint and verizon for business.
I would go AT&T if I felt like it. But I'm happy with tmobile.
All cell carriers offer a 30 day trial so why not use it? Search for the phone you like/want and whoever is the carrier, just go with it. You'll know in two weeks If service is good for you or not. If not, try the next wanted phone on the next carrier, and so on.