If you want to shoot IDPA for the game, then run a G34. If you want to shoot what you carry, then run your CW9 (in my case) but don't expect to smoke the guys running G34's. It's all about what you want to get out of the match. I ran an IDPA club for 7 years, and shot a G21, G26, G19, G17 and G34. For me, the challenge is to run the CW9.
For example, even though it is not required to shoot the IDPA classifier from concealment, I can run my G17/G34 into the 90's from an IWB holster at 4 o'clock position, but the best I have done with my CW9, from an appendix IWB, is in the 130s.