I've got a Kahr CW9. Don't for a second think that the CW series are poor quality, they definitely are not. Kahr don't make crap!!!!
They made some changes to lower the price over the P9. Let's be fair and state that some of the parts are less expensive in the CW vs the same parts in the P9. NOT CHEAP! As for the barrels, the CW9 uses the old fashioned ballard style rifling, rifling that has been used for many many years, still is, and it works just fine. The P9 uses polygonal rifling, a newer process that works better, but costs a lot more. The CW9 is a very fine little pistol, the price not withstanding.
The CW40 is just a little more powerful version of the CW9, and just a little larger, not much!
I really like mine! Especially since my wife took my Ruger SR9C.