Well, I certainly can't ... and won't ... pretend that I can offer a definitive answer to your question, but I'll add a personal experience.
One of the guys at work has a K40. He's one of the handful that actually enjoys shooting, and shoots a lot. If he's not down at our agency range on his own time practicing, he's out attending the weekend IDPA sessions each month. Nice to see ...
Anyway, he's owned his K40 for several years, and has used it for a reasonable amount of training. Other than needing to replace his recoil springs, I'm unaware of any issues he's had with it.
I found it pleasant enough to handle and shoot, and certainly accurate enough. The Kahr triggers can be nice ... if you like DAO ... although they certainly wouldn't be
my first choice. But that's just me.
I've had more opportunity to shoot another fellow's MK40, and I don't care for it. It crosses over that fine line ... for
me, and apparently for the owner, as well, watching him shoot it a few times ... where diminutive size is obtained at the expense of controllability and manageability. Some owners will naturally disagree, and that's to be expected, and perfectly understandable. To each their own ...
I'd own the K40 before I'd own a MK40 ... but then, I wouldn't personally own a K40, either. Not compared with some other compact platforms available. I'm not trying to dissuade you, mind you, just stating my preference.
You say you're a Combat Commander owner & shooter. Me too. Have you fired any of the steel framed Kahr models chambered in .40 S&W? Feeling comfortable and good in the hand at the counter is one thing, but sometimes it doesn't necessarily translate over to the actual shooting of the handgun.
I wouldn't have said this even a few years ago, but I'd own a Glock before I'd own a Kahr.
As a matter of fact, I recently bought a G26, and I liked it so much ... for what it is, mind you ... that I've ordered a G27. This doesn't mean I like my S&W's, Colts or Rugers any less, of course. It's just that as an armorer for the Glock, as well as the S&W TDA, Sigma & SW99 series, I can appreciate the Glocks as fine, serviceable, accurate defensive pistols.
I haven't reached that point with the Kahr line up ... not yet, anyway.
Didn't mean to babble ...
Best of luck, though, and let us know how it works out for you. What's life without a little adventure?