Hey Sisk. I'm 21 and was in the same boat as you. I finished college, got a job and bought a cr250. I'm 6'0 and 246lbs. I never rode a dirtbike till I got mine. Well, actually I rode a cr50, lol....
Anyways, my opinion...If you know anyone that rides, go spend a day with them and ride... If they got 125's or 250's try them both out and go from there. I wanted to go 4 stroke, but i know i'd be breaking stuff left and right since i was new to the sport, and it's cheaper to fix a 2 stroke then it is a 4 stroke.
Anyways, not sure if this helped, but i thought i would share...
Have a good one....
PS. These guys and girls on this website are cool, they really help you out, if you ask the right way.... Good luck..
Kevin