Karl passed along this video comparing a Smith & Wesson M&P Shield with a Kahr PM9.
It’s a pretty good review, showing how they compare. Not a lot of bias here.
I agree the Shield is a little big to be a small gun and a little small to be a big gun. But if your primary is an M&P, skills transfer to the Shield is much less of a jump than to the Kahr. But the Kahr is really small, and my understanding is once you get a Kahr running (some seem to burp during the break-in period) they’ll run like a champ. And while their triggers are long DAO’s, they are VERY smooth and quite nice.
I have been curious to own a Kahr. I have no way to justify the cost (vs. all the other expenses in my life). I really liked the K9 and would love to own one some day, just because. I’ve shot some Kahr’s that students have brought to class and always like them (other than the LONG trigger).
I’ll just say, if you buy a tiny gun like the PM9 for carry, do practice with it. Be sure you’re proficient with it.
Stuff From Hsoi 
“I have been curious to own a Kahr.”
I’ve owned two Kahrs in the past. Two of my friends have owned them as well. Out of those 4 pistols, 1 had a poorly machined slide stop (but still functioned) and 2 of them had catastrophic malfuctions that rendered them non-funtional. Both went back to the factory to be repaired. I quickly sold mine after that, but my buddy kept his. A few months later he experienced another, unrelated, catastrophic malfunction that turned it into a single shot pistol. Another trip to the factory and he was GTG. He now carries an M&P . . .
I hate bad-mouthing companies, and there are lots of guys out there who seem to have Kahr’s that run well. Perhaps we just experienced some QC issues that have hopefully been rectified.
I’ve heard that in the early days, their QC was bad, but they’ve really picked up in recent years. Also that if something is going to go wrong, it tends to go wrong in the first few hundred rounds… send it in, they tune/fix, send it back and GTG.
Obviously YMMV.
I mean, I even think about my M&P. Sure it’s been reliable, but it shot like crap out of the box… many contribute it to the barrel and some quiet fab changes S&W did. But it took me a while to get things running right and then feel confident with the gun.
In the end, every gun has stories like these… tho yes, some are more frequent than others. I do know a guy that carries a Kahr on a regular basis and has for many years and it runs like a champ for him. So I guess it’s like any tool: if you’re going to trust your life to it, vet it throughly first. But always remember, it’s a machine, it’s made by humans, and anything could fail.