A good shooting 12 gauge slug should kill anything on this continent, but you will have range limitations. If getting into comfortable slug range is not a problem, it will kill a pig just as dead as anything else. Then it's just a matter of what you feel more at home shooting. My bud killed a huge Russian boar up at Nugent's ranch in Michigan with a smoothbore 870 Express slug gun with no problems.
That's my 2 cents anyhow.

rw