My buddy has had both the Ruger LCP and the Kel-tec .380's. He loved the Kel-tec but is a huge Ruger fan, so when the LCP became available, he bought one and traded his Kel-tec for something else......before even firing the Ruger. There were 2 things that he really liked about the Ruger: #1 was that the slide locked open after the last shot and the Kel-tec doesn't; #2 was.......the smoother finish, which makes the LCP very slippery in the hand-that thing slips & slides all around-a problem he did not have with the Kel-tec. He now wishes he hadn't been so hasty.
As far as the PF-9, I have no personal experience with it, but I absolutely loved my P-11. Stone-cold reliable, accurate, easy-to-carry.
I do believe that if you compare it to the Kahr, the Kahr will be heavier, but have an oh-so-buttery smooooooth trigger.
When comparing the PF-9 to the Rohrbaugh, keep in mind that the Rohrbaugh can only fire standard pressure 9mm ammo, which is nowhere near as effective as +P, and requires pretty frequent spring changes. These 2 issues may have been rectified, but I'm not aware that they have.
Many people like to dump on Kel-tec, but IMNTBHO, they have been around long enough to have proven themselves, and they have established themselves as one of the most innovative forces in the firearms industry.
Sam