I don't know that the Kahrs (and I've had several) are fundamentally better pistols than the S&W model cited. It's a good design that has improved over the years. That said, however, the triggers are typically nasty, unless it's been sent back to the factory for tuneup (which they do free, and apparently do a pretty good job.)
Unless it's had the trigger worked on, I wouldn't particularly care for it. Be sure to try it.
I think, on it's face, there is a good bit of difference in price/value: the Kahr's MSRP is about $500 with one mag -- and you're talking 3; and the S&W is about $375 with two mags. While you can discount the MSRP, because they're both used, the prices should still be quite different, and the extra Kahr mags are costly. Not an even trade...
I suspect, however, the a CW45 is NOT a fun gun to shoot. If that's the case, and you still want to move on, compare prices and ask for some extra cash (maybe $75-$125+).