Nows the time to buy - 25% discount!
I have the R9, R9 Tri and the i15 master drivers. I use the R9 most of the time because the meter is a slower.
In my opinion there is little difference in performance between the 3 of them. I wouldn't take much notice of the extra 3 yards, I've played using a Tri at St Andrews and been consistantly out-driven by an opponent using the standard R9 master driver.
I would definetely go for the standard R9 Master driver, comparatively it's good value for money.