How the heck are you going to lug around enough 12 gauge rounds for your shotgun to be "versatile" in a wilderness setting?
Really, I duck hunt out of a kayak and 3 boxes is a PIA. Your gonna carry a 12 gauge that weighs twice what a .22 rifle weighs and then add about 4 lbs for every box of 25 rounds depending.
The question was if the .22 is the most versatile for wilderness/urban survival. It's not, end of story.
I never said the shotty was easier to carry, easier to carry ammo for, or even that it would be my choice. Just that it is the most versatile.
Now I am guilty of only answering half the question, just as most of the responses did -- the wilderness question. For the urban setting, it's a horrible choice. You'll do next to no hunting in the urban setting, almost all of the gun play will revolve around defending against humans. Assuming this is not a free-for-all end-of-world scenario, a handgun in 9mm-45ACP, revolver cartridges inclusive -- is the ONLY choice due to the need to conceal.
For the most versatile in BOTH environs, taking into account the need to conceal in the city, would be a 4" or 6" (depending on how much you can conceal) .357. You can deal with 2 legged problems, 4-legged problems, you can kill most big game, take a couple of 10-round packs of CCI shot shells, and you can take small game fairly well.
I'm going to take my chances with the .22 and snares as you suggested.
Actually I suggested snares and traps in lieu of the .22. I've done a lot of thinking on it, and If I was purposely going out to survive for a given time, I wouldn't bring a .22, unless it was as a handgun secondary to a rifle.
If for some reason someone sacrificed 33 1/3 virgins to the volcano, and God came down and said I had to pick a rimfire to survive with, it'd be a .22 Magnum.
Better ballistics (by far).
Almost as light.
Much better power.
Real bullet jackets.
Varminting bullets (if desired), shot shells, and the .22 WRF if you really must tone it down.
Not to mention reliability. I've always had more than a dozen duds in every bulk pack of LR I've bought. i will not bet my life on bulk pack ammo. The "Good stuff" .22 LR costs the same as .22 Magnum, so no real savings there. Even then, the .22 Mag is still cheap compared to anything but LR.
It's not as accurate as many calibers, but it IS accurate enough.
It's not as powerful as some calibers, but it IS powerful enough.
Subjective based on your needs, skills and how well your firearm shoots.
.22lr has been filling the pot with rabbit, squirrel, groundhog/Marmot, prarie dog, coyote, turkey and darn near any other animal up to about 50 lbs pretty effectively for a long time.
Never argued that.
In fact, that's why I mentioned it's a great gun to use foraging around a fixed place where you have enough ammo stored to take shots at game, and/or preserve larger animals. It always has been (I'd still prefer the .22 Mag

).
While the 12 gauge IS a more versatile firearm (the not disagreeing part), it is not the best, in my opinion for non-defensive wilderness survival.
Again, the question was of versatility, not what was best.
however, based on your arguments, it really only falls short for the long-term survival situation. Not the planned short-term situation.