When "testing" chairs for dining room suites, I found that a well formed, bare wooden seat is more comfortable that is a flat seat with a pad on it. Better fit engages more of the rump (a curved seat that fits a curved rump), meaning more skin-covered is area supporting the given weight. That translates into lower pounds per square inch PSI all over. Lower psi means fewer - ideally, no - pressure points that hurt after a short while.
Of course, if that seat has a cold beer nearby, the shape of a seat becomes less important. :wink:
Also, if there is a wild, bagpipe player roaming around to scare unsuspecting folks, the shape of the seat is totally unimportant. (Long story behind that one. Ask Piper San)