I don't enjoy recoil any more than anybody else, but I'd go with the 12 Ga. I shoot my slug gun maybe 5 shots a year. I normaly just check the scope with a couple shots, then shoot a deer or two. I really don't notice recoil when shooting at game, so it's not a factor.

I think a pump gun is more versatile in 12 ga, but if this is to be a dedicated slug gun maybe that doesn't matter to you.