If you arent used to a manual clutch and shifting gears you might want to go with a sport quad over a dirtbike. Clutching, shifting and trying to stay upright on 2 wheels can make for a steep learning curve.
At least if you bought a sport quad and master clutching and shifting and THEN got a dirtbike the learning curve wont be as steep.
Cap'n

 

ehh throw his butt on a dirt bike and learn it is easy when in doubt gas it works for me [img]i/expressions/face-icon-small-wink.gif[/img]

 

I would just get a sport quad because I know they are a lot easyier to just mess around on since I wouldn't have to keep my balance, but I really want to learn to ride a two wheeler so I can eventually get a street bike.