Hi Albert!
well there are differences in the two chassis certainly.
For 09 the KX250F was completely redesiged ,
even from the 08 KX250F..
so the 2008 KX450F and the 09 KX250F ,
have some pretty fundemental differences in a lot of ways?
steering head angle, rake and trail.
plus the ergo's of the two bikes are bit different as well.
the 06-08 KX450F is a fairly large motorcycle in overall lenght and seat heght.
and yes, I think any rider can feel differences between an 08 KX500AF
and the 09 model.
Most of those differences would be positive, as i went to that new chassis for its handling ..
so i think you'd feel the 09 model a bit quicker turning than the 08..
and just easier to go where you want it to.
but there would be plus and minuses to both bikes for a given rider? or a given type of roiding?
for larger guys, the ergo's of the 06-08 might feel better
n din some ridinfg scenerios th 06-08 450F chasismight be more suitable as well..
they are different flavors..
same great engine
have you read the MXA test? i have not seen it yet,
its in the May 09 iussue