best carrier for the iPhone

Okay so I'm curious who's everyone's carrier and why did they pick it. If it's a reason like stuck on a family plan with someone then who would you have picked as your ideal carrier if ever doing an individual plan?

I'll start, I currently have AT&T and stuck with them because I get a 25% discount with my company as well as have a grandfathered unlimited data plan. Lately, I've been considering T-Mobile because of their whole "uncarrier" thing and the simple unlimited plans. I think T-mobile is the ideal carrier for the iPhone because you get everything including tethering included and if I have an iPhone, I want to be able to use any feature I want without being restricted like AT&T does - I currently can't get tethering and in order to be in a similar price range bill wise with t mobile, I don't get unlimited minutes and texts. Sprint is also another viable option but I hear their speeds suck. So What do you all think?