I can't give specific opinions on what tab is best for the ones your considering but for your needs specifically, on cross country bicycle ride, I can give some input on what I would want:
-light weight (every ounce counts on a bike)
-compact (for me, a 7" tab is perfect for what your describing)
-durability, if you can afford a higher end brand it may give some safe guard against the tough environment but price point is not always an indicator of durability / reliability, is there a "Tough Book" of tablets?
-don't know if I would do it, but I have heard of riders using mounts on handlebars for the 7" tabs
Good Luck on finding the right tablet and on a safe ride!
PS: I'm also doing research on carriers. Apparently in the middle sections of the country I'll only have coverage with Verizon. I'm planning to buy one of their hotspots on E-Bay and then just pay for a couple of months of service while cycling
do you have any more information on this? I would love to just get an affordable dongle / hotspot device for Verizon towers without a contract, as much as I dislike the greedy V I love there coverage!