I do agree the thumpers have a higher center of gravity. My 450 also feels much heavier than my R, but it doesn't wear me out as fast. If I was drag racing or racing TT where you're screaming all the time I'd definitely prefer the 250, but for MX, especially if the track has huge jumps right out of corners, I'd take a 450.
Can't believe I'm on here defending four strokes - lol - but I really enjoy mine, although I'll never get rid of my R.
That's what my husband keeps telling me about the 4 strokes, it's a lot easier to just roll into the throttle to jump the jumps. On a 250R you definitely can't wait until the last minute to decide whether your going to jump or not. You gotta work for it a little more, lol. I think you learn better clutch skills on a 2 stroke. It may not be as important on a 4 stroke, but good clutch skills really help out in adverse conditions or in the case of a missed shift :blink:.
I do think as far as jumping goes the ease of the 4 stroke power gets a lot of inexperienced riders into trouble, and some of them start jumping things before they're ready to. I've tried to give some of the younger riders some tips, but I guess I come off sounding like their mother or something

. After the last girl bounced herself off of a 400EX doing exactly what I told her not to do, I give up, lol.
If I was going to ride recreationally in the woods, especially if I was going up and down a bunch of steep stuff I would want a 4-stroke with a push button start. But for racing giving me my Rs with a kick start any day

. Barring something just outright breaking I know my Rs will soak up just about anything I can do to them.