I gotta start paying more attention to these posts before I reply
I've have owned the Glock 27, P9, and other Kahrs, and I've found that (redundant statement imminent) it depends on your preference
. The G27 was GREAT, but it was too fat for my tastes. Then I bought an MK40 sight unseen after falling in love with the MK9 I bought my wife, but it was too HEAVY! I don't know why, but the MK9 just FEELS lighter to me. Then, I sold it, and bought a P9, and I'm QUITE happy with it. Of course, these days, since I prefer the .40 over the 9mm, I'm CONSIDERING selling the P9 for a P40
Decide how you're going to carry it, then ask the gunshop worker if you can check the fit and comfort of the gun with your carry method. In the 2 shops I go to, they always let me. I can stick it in my pocket, IWB, whatever. You could offer up your wallet on the counter, as a sign of good faith, depending on how well they know you.