The TMob senior plan does not lack data. Unlimited and unthrottled until 50 GB. It is the exact same plan for data, 480p video,, slow hotspot, slow international, and 1 hr GoGo access as their lower tier regular unlimited plan less the free Netflix subscription. All for $50 for single line, $75 for two.
Sounds like a good deal. Where the senior plans lack is Data and I think streaming is limited to 480p. It says unlimited but where it is limited is video is SD quality not HD quality. I'm not quite senior age but getting there so I noticed that plan when I saw it advertised.
Service all depends on your area. I have used AT&T for years. I get service most places. I read T-Mobile uses the same towers so I am assuming they would be decent as well. Have no experience with Verizon, but there have been occasions when my Verizon friends had service and I didn't, or vice versa. No plan is perfect. I have another friend on Sprint and his service always sucks.