Pocket pistols are going to be various sizes, mostly dictated by the caliber you pick.
For pocket-size, I like my Glock 42 .380. I also have a derringer revolver that's a .22LR 5-shot. I have a leather holster for it, but I also have a hinged grip/holster I like better for the larger grip.
I have the S&W M&P shield 9mm, but can't see that being pocket carried unless it's in a jacket or vest.
From experience, the pocket size guns will be more difficult to shoot. Small grip, usually with no room on the grip for the pinky, short barrel, muzzle flip tough to manage ...
The G42, to me at least, is a great compromise between size and ease of use. I added a pinky extension to the mags that doesn't make the gun that much harder to conceal. I left the extension off one mag just in case I found a situation where it needed to be smaller. The length and overall size is slightly larger than some comparable pistols, which to me is a plus. The larger size along with the less peppy .380 vs. 9mm makes the G42 a very good shooter for being so small. I can land all 5 rounds in one mag on paper with an 8" target at 25 yards, For a pistol that's designed for short-distance engagements, that's actually pretty good accuracy.
If you aren't adverse to off-body carry, Maxpedition has many products with Concealed Carry pockets and features. You can also go to sites like the NRA store and check out the leather planner they have with a CC section that locks.