Mozart,
I own a P-11 9mm and have shot the P-40. While all Kel-Tec pistols will benefit from the "buff and polish" routine, it's not absolutely necessary on all of them. If you're not happy with reliability you can always opt to send the pistol back to Kel-Tec for repair instead of working on it yourself. Their customer service has a very good reputation.
Yes, the 40 kicks a bit more than the 9 but I didn't find it unpleasant. I might if I had shot it more than 8 times though.
The benefit, to me anyway, of the 9 over the 40 is that you can get S&W model 59 hi-cap magazines that fit right into the 9. Kel-Tec even makes a slip over adapter for the mags so that when you use them you have a full size grip.
Joe/Ga