searcher, let me chime in here as well

I had a Kahr MK9 and presently have a R9S. This is how I see them stacking up ...
» Kahr can fire +P's. R9 can't. Is this important? It could be. +P 9mm's brings the performance of the caliber within the same range as a .40 or .45 -- if they expand the same and penetrate the same and displace the same amount of tissue, they're effectiveness is going to be the same. The same thing can not be said about the non +P 9mm.
» The R9 is a true DAO gun while the Kahr has to have it's striker pre-set in order for it to fire. It this important? It could be. According to reports that I have read, if a round fails to go off because of a light primer hit, in over 50% of the cases, a second strike on the primer will set it off. With the R9, all you have to do is pull the trigger a second time and you have a better than 50% chance of shooting the gun. With the Kahr, you can pull the trigger all that you want but until you re-set the striker, the gun will not fire. This could be VERY important if you find yourself in a struggle. With the Kahr, you might as well have a hammer in your hand. With the R9, you've got a better than 50% chance of being able to fire the gun.
» Overall accuracy goes to the Kahr. This is independent of the guns themselves. What I mean by this is that I can get a better grip on the Kahr and it's extra weight helps absorb the kick better and therefore I can fire it better. From a rest, reports place the accuracy of both guns about the same but because of the factors that I mentioned, I feel the Kahr is more accurate.
» The factors which makes the Kahr a better shooter in the point above also prevents it from being a true pocket gun requiring it to be carried in a holster for true concealment. Not so with the R9, it is a true pocket gun and can be carried when you're "not carrying".
So far both guns are pretty much even -- scoring different points in different areas. What ultimately swung me over to the R9 over the Kahr was the fact that I didn't like this internal striker fire design. Things could be going on in there that I am unaware of and might become defective without my knowkedge. I don't like Glocks for the same reason.
The R9 has a concealed hammer. You pull the trigger and you see the hammer rise and fall similar to revolvers and TDA/SA guns. That's what finally sold me on the R9 over the Kahr. Your requirements, obviously, might be different from mine but I hope this little checklist helps.