I use the G10's with Tour SD balls quite a bit and while they're easier with Callaways, they're still manageable at full speed.
I have the R9 and get on great with it. I wanted to rent both but tried the R9 first and was so impressed I bought the company. It really does shave as close as a blade, or your money back.
Oops, I turned into Victor Kiam for a minute there. It's so annoying when that happens,especially on a bus or flight. I tried to buy Lufthansa from a stewardess the other week.
Anyway, I'd do what I didn't regarding drivers; rent both and see which you prefer. What's right for me isn't necessarily right for you.