The difference between an R8 and an R9 is the price and the top. Brightness will depend on each guitar. There are R9's that are brighter than R8's and vise versa.
I agree with BadAssBill. As well I should with a name like that.
For example, I have both an R8 and a R9 and my R9 is definitely brighter sounding than my R8. It will vary from guitar to guitar as opposed to specific model.
The difference between an R8 and an R9 is the price and the top. Brightness will depend on each guitar. There are R9's that are brighter than R8's and vise versa.