the 650 is actually a good beginning bike… its probably on the same level as the SV650… which is a highly recommended beginner bike (although, like the SV650- it may have to much power for someone not comfortable on two wheels like a bicycle or dirt bike)
the throttle is really smooth and the posture and suspension are really forgiving.
I heard from someone that the 650 has more mid range power than the 500 (which has a little more low end torque) . Although, I don’t know if that is true or not. Both bikes can get you into trouble… but I think the difference in that regard is rather negligible.
With that said… I was way more comfortable sitting on a 650 than a 500- and In the end, that was what made me make up my mind, cause in reality they are very similar beginner bikes (with the exception of cosmetics and a couple of details)
I have the 650 and I think its a rather solid beginner bike– as well as I bike that I can grow into in terms of skill level.