I have ridden the 400, 426 and the 450. the 450 feels more nimble...the 426 and 450 have huge power advantage over the 400. both the 400 and 426 have a definite "big bike" feel to them... i have often commented that it feels like you are riding a pig....wide between the legs, and a heavy feel. the 450 feels thinner, and a bit taller to me, not as cramped. feels like it gets me up and out of harms way, and does so while feeling more nimble. i also feel that the lower seat height of the NEW 05's gives me the same cramped feel of the older 400's and 426. feels like my knees are TOO bent when up on the tank. all of them are stellar bikes with only subtle differences in ride and feel. i happen to prefer the 03-04 model 450's...with a leaning toward the 04 model due to starter refinements.