I've had my P3AT for a few years now and have been very happy with it. I have the clip on it and use it all the time, it is very convenient and as long as your pocket is loose enough that the gun doesn't print it looks like a knife clip.
I saw a LCP for the first time the other day and, while it is a nicer looking gun, it is just a knock-off. If it was me I'd buy the Kel-tec, IMO the Ruger isn't worth the extra money or the wait.
BTW, the P3AT does not have a slide lock and the LCP slide lock has to be set manually, neither gun locks the slide back after the last shot.