There's lots of fun to be had on an SV650, I had an 06 for my hire bike after a lady reversed over my YZF and it was nice to ride. The little Vtwin engine has a surprising amount of 'fun' torque and can easily 'force' you to accelerate hard to hear the induction etc, I was almost sad to see it go back to the hire company.
The front end is a bit twitchy at speed though, but that's probably down to the budget suspension and could be fixed with some tweaking.
Still, the CBR600RR would be alright, as long as he doesn't go straight out and start trying to get knee down etc.