"All calling and internet access"
NOT accomplished through wifi. For someone often removed from free wifi, this option is not as favorable. I just about live in free wifi so I sometimes have periods where I don't need 5G at all without feeling like I'm missing a thing.
Cellular data calls (and texting) do NOT eat much data at all. I run a business and travel for business and have never got close to 5GB. In my experience, 5GB is small for video streamers (on cellular) and heavy cloud users (music renters for example). Calls & texts use very little data. My dominant data eater is Safari.
Prior to this Tmobile plan, I did have a 1GB/month data plan and only ever bumped into that limit in one month over a couple of years (due to travel and sharing data with some others). When I did, I just immediately purchased another 1GB block as I could do with this 5GB if I ever bumped into that limit.
If I was an iPhone user, I'd probably be seriously on that Tello offer. $100/yr vs. what averages more than $110/month is also a BIG difference for iPhone users... especially over a couple of years.
I don't really "keep checking" (capacity usage) as I've basically trained myself to manage data use. It's pretty much habit now. And there's no worry at all about running out as I can just buy another block of 5GB if I ever do.
Portability is an absolute issue to this option. iPad Mini is NOT as pocketable (suit/coat pockets only). I tend to just tuck it under and arm if I want hands to be free... OR... leave it in the car and fully detach when I don't think I really need it. The world continues to turn if I'm not continuously connected every time I do that.
We all should try that from time to time.
If there is ever an iPad Mini Fold/Roll/Other to potentially address iPhone-like portability, I'd be pretty interested. I'd also be very interested in iPhone Max cameras in an iPad Mini Pro... along with some of the other features referenced earlier in the bullet list of things that this option doesn't have vs. iPhone.