Neither.
As subcompacts, they're both too big for front pocket guns.
The Kahr is a tad smaller at the expense of 4 rounds capacity.
If the price difference between the Kahr and the Kel-Tec isn't off-putting and you want a 9mm pocket gun, wait until after the SHOT Show in Orlando a month from now. Rohrbaugh's debuting its R-9, a 9mm pocket pistol the size of a Kel-Tec P-32. It will cost about as much more than a Kahr as a Kahr does than a P-11. R-9s are stainless and aluminum weighing less than either the Kahr or P-11.
At the same time, Kel-Tec's debuting its P-3AT, a P-32 size, price, AND WEIGHT .380 ACP.
The two most powerful locked breech pocket pistols will then be the 9mm Rohrbaugh, and the .380 Kel-Tec.
IMO, a front pocket pistol is something that should be able to be drawn in complete stealth mode, i.e., without telegraphing you're producing a pistol by any hand, arm, body, or clothing movements. A bunch of different compact and sub compact pistols can go into pockets, but very few of them can happily stay there all day and be drawn in a flash. The only guns I'm able to make appear as if by magic are mouse guns the size of P-32s or less.