125, but just look for the best deal. The 250 will have more power, but they will both put you on your butt if your not careful. Shop around for a good deal and the 250 you can "grow" into.
IM 5'8 225 stocky build and i alwayz loved dirtbikes but never had the money to enjoy them but times are different now and i want to know what is the best bike for me to start with im a beginner but a fast learner i dont know if this helps but i know how to drive a stick a little. LET ME KNOW YALL
Hell KX 250.... it ain't fun unless you can hurt yourself lol. Nah I think you can handle it. You being 225 isnt really anything the 125 couldn't pull. But as long as your feet touch the ground it will be ok.