For a number of years when traveling in the mountain west, we had both a Verizon MiFi and used the hot spots on our AT&T iPhones. What really helped with both was when I installed an external antennae and a Wilson Sleek rig inside our RV. Business may it a requirement I felt to be able to stay in touch with clients. There were time in the west that neither carrier had a local signal that we could find, a couple of times both had a voice signal but no data signal was showing up. The external antennae solved most of my connection problems if there was a usable signal.
A couple of weeks back we were camped in one of the more remote Florida State Parks, where I saw a man sitting on his roof, laptop and hot spot running. He commented too, that an external antennae might be the way for him to go. LOL