I don't care much for running into feral hogs or true wild boars one bit, especially if there are a bunch of piglets around. Even domestic sows get aggressive when they have babies around.
I don't have any experience dealing with feral hogs since all of them here in Missouri are south of the Missouri River and I am north of the river. I have had to deal with the wild boars while stationed in Germany. Now those do get big and mean and I would want something with a lot of knock down power.
Now dealing with domestic pigs most of my life, pretty much any good self defense round should do the trick. Yes it only takes about 6-9 months for an excepted domestic pig to go feral and start to get physical changes. But I wouldn't feel under gunned with a 9mm with good defensive ammo.