Would you be able to explain?
Sure.
I use T-Mobile.
I'd consider myself a power-user, in that I use a great deal of data, I use tethering both Wi-Fi and USB, and I use multiple devices. My phones are rooted, and T-Mobile could care less. Also, I travel extensively, and T-Mobile has great travel plans and have no problem unlocking devices without charging you. I also make a lot of international calls, and T-Mobile is great for that too, sometimes even cheaper than Google or Microsoft VoIP packages.
For me alone, T-Mobile would cost ~$80/mo, IIRC, for unlimited
everything. Now is that throttled after 21GB? Perhaps, but to be perfectly honest, I've never noticed it (perhaps because I use a VPN? T-Mo's DNS security is easily defeated)
Also, I may not be getting throttled because I don't use the T-Mobile tethering application or service, but instead the native Android service.
I was a Sprint user from 2009-2013 and I fucking hated it. Sprint is trash. That leaves Verizon, T-Mobile and AT&T.
As far as speed, T-Mobile reliably gets me 25 Mbps+ downstream, no problem. Also, coverage is great. AT&T, IMHO has both bandwidth issues and coverage issues for 4G LTE.
As I see it, T-Mobile is the closest you can get to Verizon, which is admittedly the best service there is; but T-Mo is considerably cheaper.
I'd strongly recommend their service over the competition.