I'm not really a fan of striker-fired weapons, but since the .40 is a better "stopper", if I got a PPS I'd get the .40 S&W version.
I love the "slim" design, but I would really like an exposed hammer, the choice of cocking or firing the piece DA first shot, and the comfort of knowing there's a round up the spout but no possibility of an AD/ND without pulling the trigger fully to the rear.
However, I suppose that the PPS design is really the best way to get a .40 caliber round in a weapon that is as concealable as the PPK, which is a blowback design totally unsuited to the .40 SW unless cursed with a massive HiPoint - style slide. This of course would negate the concealability of the PPS.
Having said that, I nonetheless must admit that if you are after a "deep concealment" firearm in better than .380, the PPS seems to be the way to go....