I think that AAA seems weaker because of the outstanding Irmo and Northwestern squads.
3A is just under the huge shadow that is cast by the possible NW vs. Irmo final everyone has been looking forward to all year.
I think that Eastside, Mann, Chapin, and SA could compete with any 4A teams out there besides NW and Irmo and put up just as much of a fight against those two as anyone else could.