You could if you want both. I don't think a skunk or beaver that is shot at a decent range would be able to tell the difference. I can tell you for a fact, the turkeys I have killed with a 12 ga are just as dead as the ones I have shot with a 20 ga.
That is the great part of being a gun nut and living in America, we can choose either or both.
I'm testing if you guys are enablers or not. ;-)
Side story: I use #2 lead 12 ga on beavers because it pattern much better than buck shot... and I get it free. I have a friend that works at a landfill and they get people bringing in old ammo and he brings it to the gun club to shoot up and saves tax payer dollars. I don't get as much 20 gauge heavy though.
Still debating. I probably have forgotten the pain from my last shoulder injury..