40 cal. vs. 9mm
In the Kahr platform, I'd go with the 9mm. I have the P9 and it's pleasant to shoot whereas I find the .40 has a bit of snap to the recoil. I agree with the other posters that the .40 holds too little advantage over the 9mm to warrant the increased expense and recoil.
Also, if you're a CCW or primarily concerned with home defense, your needs are much different than that of law enforcement. You shouldn't be engaging barricaded gunmen, shooting through car doors or auto-glass or engaging felons much beyond arm's length.
Int'l Assoc. of Law Enforcement Firearms Instructors