Tablet install for Kenwood DNX7140?
 

So I've noticed quite a few people doing tablet installs and I thought it was one of the best mods for this car.
I have a kenwood DNX7140, and I'm looking for some advice on what the best options would be:

1. Which tablet works best? IPad mini or nexus 7? (note: I have an iphone 5 with unlimited data plan through verizon)

2. What is the best way to connect the tablet to the kenwood unit so that the unit will power on and power off with the vehicle? I'm thinking the connection would be via USB, but I'm not 100% sure.