It really depends on the riding you plan on doing.
The stock gearing on the X is 13/42, 13/43 for the R.
For a while I ran 13/47.
It was fun but I wanted to keep my top speed for faster tracks and to keep the rpm's lower on the interstate.
I went up 1 to the stock R gearing on my X and I like it.
Plenty of power for wheelies and general hooliganism.