I have 2 Glocks and 1 Kahr, but not the two specific models you are comparing. If I had to choose either the G27 or the Kahr CW40 for carry purposes, I would probably go with the Glock.
On the size comparison, I believe the Glock is a little thicker than the Kahr, and weighs a little more when loaded. But they are roughly the same size.
My primary reason for going with the Glock is that I would trust it to work more reliably than the polymer Kahr. My own Kahr is an all steel model and it works well, but I am slightly distrustful of the polymer Kahrs based on what owners of these guns have said.