I have both the G26 and P9. I got my Glock a few years ago. Then, the Kahr was relatively untried. Got the P9 about a month ago.
Glock pros: small, light, accurate, absolutely reliable, holds three more rounds than the P9, great reputation.
Cons: two finger grip; I use a Pearce extension which makes it, roughly, the same size as the Kahr grip.
Kahr pros: while overall length and height are very similar to Glock w/ Pearce extension, Kahr is noticeably slimmer and feels smaller in the hand; lighter, excellent accuracy, very smooth trigger, mine has been 100% reliable, YMMV; good reputation, the two-tone stainless steel/polymer looks killer.
Cons: Holds 3 rounds less that G26, they have had some bugs when introducing new models.
Without the soft grips of the K9, the slide stop lever sticks out more than needed. Kahr has a slimmed down slide stop lever and sent me one free. You can see it in the P Covert photos on their website. It's definitely better.
Both are fine firearms. Many of the differences are pro/con depending on your personal preferences. I like the feel in my hand of the Kahr much better. The P9 comes with the Kahr "Elite" trigger, which is a shorter, smoother pull. It is slight longer that the G26, but smoother. I prefer it.
I also have a G23 which is my home gun, but the P9 travels with me.
Tim