I like frictionless Fi is. Phone breaks? No prob. Grab a cheap Moto phone from the Fi store listing, get it in the mail the next day, and setup in 5 mins. Go over on data? No prob. Pay a prorated price at the exact same rate.
Or you could be a T-Mobile subscriber and never "go over" on data, even when abroad. It just gets slower, but that's fine most of the time, at least for me. It's amazing to be able to use even slow internet in the butt crack of the world somewhere without paying an extra dime - that's the way it ought to be on all carriers.