SX rocks, but MX is balls out tougher. I have never seen anyone pass out and need an I.V. after a SX race from exaustion. Seen it many times at the national MX races.
Rough. HOT. BIG. Long. FAST.
MX is it for me too. Most amatuer dirtbike racers will never ride a true SX track, but we can and DO ride MX tracks.
it is easier to ask for forgiveness than permission