There is a difference in the "quality" of the recoil between smaller calibers such as 9mm and .380 (9mm kurz) and the .45 ACP. Your characterisation of it as more a shove than a kick is IMNSHO right on the money. I find the "shove" of the .45 (maybe because the recoil is spread out over a longer time - even though we're talking milliseconds) much less annoying than the sharp "kick" or punch of a .380. The .380 also tends to twist in my hand (even the extension on the magazine doesn't really give enough grip) while the .45 pushes straight up and back. As I said before, the PPK's only real redeeming quality (aside from its meticulous German workmanship) is its small size and concealability.
That is a very good point. And probably more to do with the locking design (blowback vs. link, etc.), the weight, and maybe the burn rate of the powder in the cartridge, than the caliber. I also have a sexy PPK/S in .380 that I just love, but after putting 50 rounds through it, and bleeding from the webbing between thumb and forefinger, I'm looking to go do something else! (But I still won't give it up. Just wish it was a little more reliable.) Peace.