What does the slide lock on the Ruger matter? It's a pocket gun- not something one would be doing tactical reloads with... It's an "Oh $#!T" gun.
My vote would be for the Kel-Tec. I owned and carried a P-32 for quite a while, and the construction is very, VERY similar. It was thin and light enough to slip into my back pocket like a wallet, and never interfere with day to day life. The pocket clip works well for IWB carry, as well. And they're way, WAY thinner and lighter than a Beretta or NAA Guardian.
Yes, they feel cheap. That's because the grip is not the frame. The grip is completely interchangeable and the frame is a small aluminum block inside. The part just barely visible with the serial number on the back. Because of the aluminum frame, I wouldn't suggest putting a ton of rounds (10,000+) through it just for practice, and stay away from +P. Just get CorBon and you'll be fine.
There's also a ton of aftermarket support for them, like Crimson Trace or Armalaser sights, holsters, etc.
So, PROS: light, thin, affordable but not cheap, and lots of support that's easy to come by.
Will I admit to a CON? Yes. Two, in fact. If you carry like I did, sitting on it can release the magazine. The NAA Guardian, and Seecamp don't do that. The other MAJOR con, imho, is the "set double action". The slide has to cycle to set the hammer in place for the DA trigger pull. Meaning, if you get a light primer strike (which I had happen in my P32), you're done shooting. You have to manually cycle the slide to set the hammer and continue.