Join Date: Apr 2006
Location: Amity, AR., USA
Motorcycle consumer news website has some figures for both bikes. Power wise your talking 3-5 HP and maybe 1-2 ft lbs torque (same 636 cc's). Riding position is the same. The biggest difference (and in my opinion worth the extra $$) is the brakes and suspension.
'03-04's had Kayaba suspension that was harshly damped with a narrow range of adjustment. '05-'06 went to Showa forks which work alot better plus they have radial mount brake calipers and new style wave brake rotors which add to the stiffness/fade free stopping power.
05-06's have lighter wheels as well. As for styling the 03-04 is thought by many to be alittle better looking but the 05-06 has a better aero coefficient of drag as well as a tasty underseat exhaust.
Also check out the Motorcyclist website and sportrider websites for more nfo...
Been there, crashed that, Fixed again, sold it!