Either is fine. Whichever place sells it cheaper. T-Mobile's price for the phone is higher than everyone else's though. Keep in mind T-Mobile does not have LTE, but does have unlimited data. Sprint has LTE and unlimited data, but is probably a little more expensive on the monthly bill.
Thank you Toki!! So t-mobile high phone price, unlimited data and possibly lower monthly charges vs sprint lower phone price limited data and possibly higher monthly price! Thanks bud. Tomorrow is the day. Hope i don't regret it lol Excited.