I've had the p380 and currently carry the pm9. I love the PM9. I had phylodog stipple the thing and i'm more accurate with this little gun than any of my full sized guns which amazes my friends at the range considering it's size and long trigger pull. I had to polish the feed ramp on the p380 to get it to function properly so i wasn't as confident with it as the 9. I have shot some of the larger Kahrs, but they are kind of punishing. I'd go 9mm if i were you.
CM9 = my EDC. I have to admit, I was a little iffy on the idea of needing to run 200 rds through it to consider it "broken in" But I didn't have one malfunction through that first 250ish rounds.
I guess just like many finely tuned machines, guns need to be broken in a little to be %100 reliable.
I love the CM9 and would recommend it to anyone looking for a slim, easy to carry 9mm.
Lots of praise for Kahrs is justified. Great gun, and hard to beat in an IWB holster.
I prefer the "full size" (I own a P9) because I like the full grip, and in an IWB, as I wear it, I wouldn't gain anything from a shorter grip. I used to own a PM9... and switched to a P9 for that reason. Perhaps if you were carrying in a coat pocket, a "PM" would work where a "P" wouldn't... but generally, a PM9 isn't going to be small enough to pocket carry in pants.
And this is a huge can of worms, and everyone has their opinions on caliber... but I went with a 9mm. The Kahrs are so light (as are many small guns nowadays), and I just greatly preferred shooting the 9mm for purposes of follow-up shots. Also like the extra round or 2 over the larger calibers.
Finally... go with the CW9. I bought my P9 before the CW9 was available. It is a carry gun, not a showpiece. I remember reading some articles on it (and you can search yourself), but I don't think the differences are significant. Finish and aesthetics, mostly. And the CW9s look fine to me.
I have a CW 40 and its a great piece, however with that being said they are not a great first gun.Long break in period and a bit difficult to cycle due to the stiff spring early on...but great shooter, very accurate for the barrel length