This one is going to be kind of tough to put into words. The biggest difference is the "feel", but that doesn't answer your question. But I'll try.
Wakes- wake characteristics at 22 are significantly different
Angles- running 22 with shallow angles is pretty achievable. Once you get to 28 and beyond, the angle of the ski's path AND the angles of the skiers body at the ball become much more critical
Whip- simply put, the feel of the line whipping you across the wakes as opposed to having to pull all the way across the wakes.
For me, when I was running 22 off as part of my practice sets, it made me ski "lazy", shallow angles, and narrow. When I dropped it, my skiing improved. Practice doesn't make perfect, perfect practice makes perfect. And for me, practicing 22 only enforced bad habits that wouldn't work at 28-35.
Hope this helps a little.