whether you choose a 12 or a 20, I would not want to get hit by either one...their both absolutly evil creatures that will drop a black in a heartbeat. just a note, if you buy a rifled barrel slug gun, you'll be fine. If you buy a smoothbore, more than likely, it will have an imp cyl choke. DO NOT SHOOT SABOT SLUGS OUT OF ANY CHOKE OTHER THAN RIFLED!
So many people do this, and lots of salesman sell slugs to guys without asking what type of bbl they have. Guys buy them cause they look cool. But that sabot can plug up in a choke and its like shooting a plugged barrel! it can go Kaboom!