I have 2 sub-compacts that I carry. I have a Glock 27 and a Kel-Tec PF-9. In my experience the Kel-tec is much easier to conceal and more comfortable to carry due to its light weight and very thin cross section. The Glock is much heavier, thicker and is somewhat more difficult to control due to the muzzle flip. I carry my Kel-tec most of the time in a belt or pocket holster and it is almost invisible. With that said, the Glock is a far better made weapon. The trigger much better, the fit and finish is much better and mine has never had a malfunction since I purchased it in 1994 (not sure how long I have had it exactly).
If you do consider a Kel-tec be fully prepared to work with it until you can get it broken in and operating consistantly. You might even want to consider having a qualified gunsmith do a "fluff & buff" before you even take it to the range. Mine started out with about a 15-20% malfunction rate out of the box. After some polishing and an additional trip to the range it dropped to 6%. The last time I had zero malfunctions through 150 rounds. OF course there about a $300 difference in price between the Kel-tec and the Glock. So it all depends on how much you want to spend and how concerned you are about concealability and comfort. Good luck!!