I have AT&T phones with 40 gigs hotspots, Calyx Institute T-Mobile Unlimited hotspots, and Verizon Grandfathered unlimited hotspots. I check all three at every campsite and there have been two locations that had not enough services to stream TV on all three. The majority of the time T-Mobile has outperformed the others by a good size margin and Verizon has been on the low end. It just depends so much on the locations and even the part of the county you in. I RV mostly west of the Mississippi but I have been told the east cost is Verizon country.
If I had to pick one it would be the T-Mobile after they bought out Sprint they seem to have great coverage in most the the areas I RV in prior to that they would of been my last choice.