i don't know what the best is, but i know i like house made flour tortillas. if they aren't outsourced, consider me a fan. with that said, these are some I've enjoyed:
jorge's garcias? tacos
la mexicana bakery
All these tortillas are really different than those sold at Central Market which are thin and springy/stretchy, as opposed to greasy, flaky, or fluffy.
HEB also sells a couple of varieties made fresh in store as well as decent refrigerated and griddle version.
Maybe not the best, but the flour tortillas from Central Market are far up my list. btw HEB tortillas should be in the same ballpark, but are not near the same quality.
I personally really like the corn tortillas served at Angie's, but I don't know if they sell in bulk, etc