Ok so I have a couple of choices for my first new bike...a 2006 910s with 1800 miles or a 2008 910r with 3400 miles. I really love the red 06, but the pearl white/black 08 looks ok to me. How much performance difference is there really?
910R for sure!!!! the lighter wheels make huge difference to the handling, if you want to upgrade the 910S then your looking at several thousand $. The brakes are awesome and they're radial, i upgraded my 2 piece brembo radials to one piece and they are even better but with the 910R you get the radial bottoms which cost again roughly $1K if you were to upgrade the 910S. And lets face it we all want the best wheels and brakes if only for bragging rights, the 910R has it all.
The 08 Models have a few improvements, not all improvements are desirable though. For example, you can't fit a de-cat to the 08 model unless you replace all the headers as well. Also a Power commander needs to be fitted by a garage who knows their stuff or else you will have to get a whole performance ECU. But then you have more hp to start with so its still better to get the 910R over the older 910S. especially at those prices.