When I went with a small 9mm, with pocket carry in mind, I first bought a SIG P290RS and then added a lighter Kel Tec Pf-9.
Both can be pocket carried if that is what you want to do. Both are a little big for pocket carry. I also have other guns for the same job in various calibers, a couple J-frames (including the 15oz aluminum S&W 442), and a true pocket sized LCP. I have given up on pocket carry for a number of reasons (which I won't go into here).
I have also extensively shot the Kahr PM9 (the higher end version of the CM9) and the all metal MK9 since a good friend used to own them, and I often used to rent the Kel Tec P11 at a local range.
I found the P290, MK9 and PM9 the most comfortable to shoot (in that order). The P11 was OK, the Pf-9 is almost punishing and is definitely uncomfortable.
For pocket carry, any can be pocket carried. The PM9/CM9 is smaller than the P290 or Pf-9 in some dimensions, and the P290 and Pf-9 are smaller in others. The MK9 and P290 are a little heavy for all day pocket carry. Again, they are all doable. Though, if you want a gun purely for pocket carry, you may be better off with a .380.
If you want the gun for IWB, I prefer a little weight. All of these guns will absolutely disappear in a tuckable IWB holster. On the belt, the heavier guns are still quite light. However, the slight extra weight of the metal MK9 or heavy for polymer P290 make a big difference in shooting comfort, and thus follow up shot speed and control.
For capacity, I prefer the P290 or the Kel Tec P11. The P290 comes with two mags, one flush with 6 rounds, and one with an extended mag that carries 8 rounds (for pocket carry I'd use the 6 round mag, but for IWB the 8 round mag is perfect). That is quite a small package carrying 8+1 rounds. The P11 goes 2 better with a 10 round mag (though it will be slower for follow up rounds since it can be a small beast when firing it).
This is why, when in a carry state, I used to carry the P290 about 90% of the time (before moving to larger guns) and still often carry it. I rarely take my Pf-9 to the range let alone carry it, and I plan to take it to the dealer to trade or sell.