Both are fine honestly. I would say shaman is the better deck overall but there are a lot of priests out there and aggro warrior fairs much better against them.
I climbed legend with quest shaman and it went well and is super fun. It's a fairly high skill ceiling deck so if you want to keep it simple after being gone a while and smash faces then go with the warrior.
Right now i'm climbing a bit with Aggro and don't seems bad. My objective is to hit r5 for the free dust... i probably never hit Legend i'm too nub on card games ahahah btw ty for all ^^