I'm about your waist size also, and I have both the medium and the large on-hand. I've worn quite a few of both. I'm basically right at the edge on size. The medium do fit and can be taped up, but the lowers only make it to the front with about 1/2 inch of overlap on the wings before applying the tape, so it's pretty close. For my waist, the top tapes end about 1" out from where the leak guards anchor. (that's my aiming point on these diapers) The larges only move this point in one inch on each side, but they provide several inches of overlap on each side on the lower wings.
Given that they are the same cost per diaper, I'd say go with the large for now. They'll work fine for you. Some diapers don't do well when you oversize them, but these are high capacity and wick pretty fast so you shouldn't have problems with leaks if it fits a bit large on you. I don't.