It depends what you are going to do. If SQ then Usaci might be more in line withe what you like. they used to be less picky about too much bass and it helped your score in the spl portion. IASCA sq was little more about sounding real. No over doing the bass, also you only get points to up to 130-135 db. both are alot of fun
For spl read the rules (USACI,IASCA and DBdrag) and see what best suits you. All three offer a bass race type of classes too (including db drag)