My buddy Viola-tor spent a lot of money and time converting his regular 990 into a 990R. And he says its a big difference. I have a 950 that I rode off road on trials for a summer before I had the suspension rebuilt/damped/charged/valves/whatever. That made a huge difference from stock! So I guess I'm saying that either model of 990 will probably serve you well as long as you have the suspension set up by a pro.
Wind in my hair, bugs in my teeth!