In the last year I have tried all 3, 500exc, 350xcf, and as of right now still have the 450xcw. 350, not torquie, no grunt off the bottom, mid range up motor. 500, great bottom, great torque, very strong. 450, same as the 500, BUT easier to manage, can be more agressive, and less tiring to ride longer than the 500, feels better in the corners. The 350 is a good running bike, but doesn't get the adrenalin flowing with a twist of the wrist.
2003 KTM 640 Adventure