Nothing wrong with 115 grain, but I chose midpoint; and it fits into my "9mm standard round" so that it can be used in any other 9mm I may eventually end up purchasing. Personally, I believe 147g is too heavy for such a short barrel and with no +P to help even in the slightest. Not that +P actually increases speed and energy that much in say the Federal HST LE rounds (124g).
Big is slow is 45 ACP territory IMO, so that's my rationale. I also shot HST and Gold Dot because I want to have a backup round should I need to go that direction.
I'd stay away from Double Tap ammo, especially in the R9 because it is extremely high pressure from what I understand. Corbon is usually loaded hot, and it may or may not be +P. DO NOT SHOOT +P in the R9!!