Can't give any guidance on the P45.
On the CW9, I have one and I don't believe that you will be missing out on anything, unless...you want to have night sites put on it. The CW's front site is two posts that go down through the slide instead of being dovetailed in the slide. Other than that, forged slide release on CW vs machined on P9 (big deal). Rifled barrel vs Polygonal on P9 (unless you shoot competition, no biggy) CW is plenty accurate. Engraved slide and the 45 degree cut on the slide vs the P9's cosmetic features (not important at all).
If you want the CW9, go for it. I love mine.