both have increased flywheel mass stock, so both are already pretty tough to stall. I think that if like me, you are on a budget, you should go with the nicest and most well maintained for the money(that you can of course afford). Obviously the condition, year, upgrades, and your standpoint on the handling and ergos all fit in. I know a kid with a kdx200 and raves about how comfortable it is. My neighbor who is an experienced racer picked up an rmx250 to get back into racing a few years ago, and had no complaints. He did however always tell me "its just a trail bike." He eventually had to get something newer and faster to compete, but bottom line look for the deals for a maintained machine.
Alex