4a is the toughest hands down, from regionals to placing at state. Winning state is just as tough to do if not a little bit tougher depending on the weight at 6a. I don't know too much about 321a except that it is the only class besides 4a that has 16 man brackets at regionals. It is easiest to qualify for 5a state without a doubt, but a state champion is exactly that and I wouldn't want to take that away from anybody.