if you get a chance, auto X has alot of the road course experience to be gained except you're only on your car hard for 1-2 min at a time MAX, where as on the track you may be out for 20 minutes running pretty hard the whole time.
if you're into drag racing that's a whole different game that I personally have no interest in getting started, but tons of people like it and it's a safe environment to go enjoy your car.
as far as seat time per event
drag racing<auto X<trackday, although as far as cost and wear on items like tires go it's probably the reverse order
it's too bad that BMW has made a car that owners have to worry about overheating on track, even without computer tuning for the turbos. Unfortunatly it's just what BMW is doing lately, going more towards tech and gadgets and getting away from building trackworthy cars.
hopefully the 1 series will be what the 3 used to be when it shows up