I have a G23 and a KKM barrel in .357 SIG. I have switched to 100% .357 SIG. Both calibers have been flawless through my G23, with 2200 rounds so far (50/50 split).
Since the guns are identical, it really makes no difference as far as mechanics. In my case since I have grown so fond of the .357 SIG, I sorta wish I had bought a G32 just to have .357 SIG on the slide. On the other hand, if you decide to resell at some point, a G23 will be easier to sell and likely fetch a higher price.
For your stated purposes, I'd recommend going with a G23 based on the resell advantage.
Btw, I think a G23 is the best all around handgun, especially if it is going to be your only handgun. There is none more versatile!
Last edited by Markel; 01-19-2013 at 14:39..