I have the KT P3AT, PF9, and the Bersa T380.
P3AT is, IMO, the best pocket gun for the money in existence. With a decent holster, you've got 7 rounds of 9mm kurz on tap in something that looks like a wallet in your pocket. It is larger than the NAA minis, but holds a number of advantages (to me, it is quite accurate...very natural to hold...and higher capacity and larger bullet). Which isn't to say I wouldn't want one of those NAA minis!
The PF-9 is stretching the limits of pocket carry and would work better for those that have larger, loose pockets. It works good for me in shorts.
The Bersa is larger still than the PF-9, and while I love the Bersa, I think it might be pushing the limits to call it a pocket gun. Its the most comfortable and fun to shoot of the three, and it is my wife's defense gun right now. If you are considering one of these for pocket carry, by all means try it out at a gun store, using a holster if possible, before buying it, as I would be unable to pocket carry this gun, myself.
I love all three...I carry the PF-9 when dress permits, and the P3-AT, all the other times. It really is a go anywhere sort of gun. If you want a lighter recoil gun, consider the P-32.
Obviously there are other great pocket guns...the Rohrbaugh if you're feeling rich, the NAA Guardians if you can handle the extra weight, Seecamps (also a bit pricey), and the traditional J-frame snubby. I'm not saying the P3AT is better since I don't own those, I'm just saying I've been enormously happy with my purchase, and I've carried the thing for the majority of my hours awake since acquiring it. Good luck with whatever one you get! And if you get a Kel-Tec, and have trouble with it for some reason, you might check in at KTOG.org, where a lot of the guys are very experienced and can help with minor problems.