I don't pocket carry, but if so I would choose the G27 because the G26 is the same platform as the G27 and you get more caliber. The G30 is bigger than the G26/27 in height and the slide is thicker, and is definently not a pocket gun in my opinion, but you can't beat .45 on the street. I never fondled a G36 but the slide dimensions are about the same only you lose rounds with the single stack (is 6 of .45 enough?).
I carry a G23 IWB and sometimes agonize over carrying the G30sf instead - the dilemma is .40 vs .45 and 14 vs. 10 rounds. And we could discuss target reacquisition and accuracy of different barrel lengths, but I'll save that for another day.
And to answer the original question, I don't consider any Glock a pocket gun although I can conceal my G23 in my front right pocket of my dress pants. But I think carrying any Glock (any gun?) without a holster in a pants pocket could offer some unwanted surprises.