agent00: Go with the 12 GA. I live in Switzerland and I have a doublebarrel shotgun in 20 GA and shotguns in 12 GA.
20 GA ammo is harder to find, there is less choice and it is more expensive.
From my point of view there is no good reason to buy a 20 GA if you can also buy a 12 GA.
Buy ammunition from different manufacturers and compare the felt recoil. There are huge differences.
Yes it is the same here in Austria. 12 gauge widely available and 20 gauge rather hard to find compared to the plenty of different loads available in 12 gauge.
Trying out different manufactures is also good advice to compare the recoil. I was planning to that as well.
I also want to try out different slugs. Only for target shooting though. For sd I will either use some heavy lead or stell birdshot or 00 buck.
@All speaking of steel shot. Can steel shot be used in any shotgun or does the shotgun need to be certified for it.
As a layman I would say that due to the fact is harder than lead it migh be bad for the barrel but maybe I am just overthinking things.
I have read online that certain guns have special marks for steel shot online but my prefered shotguns
Baikal MP-43KH or the standard baikal guns does not seem to have such certificates.
I am unsure now if steel shot can be used.
@Neveda Ed thanks a lot for submitting the recoil numbers.
The difference is really not that big when the recoil numbers are concerned. Considering the better availability of 12 gauge rounds in my country the 12 gauge is the better choice for sure.
As I have said I already have decided that is going to be the 12.
The only remaining question left is which gun it is going to be. the 2 baikals or the stoeger double defense?
The 12 gauge coach gun from Uberti would be a honrable mention. It would be more expensive than the other choices but I really like the classic look of that shotgun. I like these old west type revolvers and also rifles.