I feel that I have an experienced, yet unbiased, opinion on this. I have owned a 97 620 Duke and an 06 950 SM. I own neither now.
The 620 was a great play bike, but just didn't have the legs to be any kind of a bike to take a real ride on. And those earlier LC4 motors as used in this Duke, vibrated quite a bit.
If I were told I could re-own one of these bikes today I would buy the 950SM. I wouldn't even look for/at a Duke. Hands down, no question. Shorter around ton rides or longer trips, the 950 was better in all regards.
Brents347 Truckee, CA.
07 Yamaha R6
07 KTM 950 Super Enduro
04 KTM 250exc- plated two-stroke