I've owned a PM9, and currently own an MK9 and a PPS.
If you want pocket carry, the PM9 has lesser dimensions in length and height than the PPS, and will carry in more pockets.
The PM9 is pretty accurate, but the PPS in my experience is slightly more accurate than the PM9 or the MK9.
The PPS is easier to shoot rapidly than is the PM9, as it affords a full three-finger grip. The MK9 (which you didn't list, but is the all-metal sibling of the PM9) falls in between, as its all metal weight absorbs recoil and negates some of the top-heavy feel of the PM9, but it still only allows a two-finger grip unless you use the extended magazine.
I have NOT had good luck with the PM9 or MK9 and extended magazines. My little finger's leverage on them seems to affect feed reliability. I have not had a problem with the flush fitting magazines, other than a reduced ability to keep muzzle flip down due to my little finger hanging in space. Note: The PM9 and MK9 are both torquey little guns under recoil.
The PPS allows three different magazine lengths. I have had ZERO failures to date with the PPS.
I am not a fan of the "safety" feature built into the PPS grip - if you detach the backstrap, the gun is disabled. In theory, this prevents accidental deaths during disassembly. In practice, it could disable the gun under some (unlikely) conditions. My partial solution to this was to install a LimbSaver grip sleeve, which helps guard against accidental detachment of the backstrap, and which also helps fill my size L/XL hand a bit better. (I use the large backstrap on the PPS.) Coincidentally, the LimbSaver grip sleeve also damps down recoil, which isn't really bad in the first place in the PPS.
Of the three guns, I'd go with the PPS, but it is better in IWB mode than in pocket mode.