I hunt alot of hogs on the homeplace in Texas and here are my general conclusions.
They have a fairly keen sense of smell, hearing is pretty good, but eyesight is poor.
My hunting is along the Red River, in brushy conditions (mostly), and often at close quarters - I like to stalk, look, and listen.
Under these conditions, a bullet that can take a little contact with grass, leaves, or briars is helpful.
I agree with the assessment that a well place shot with a small, high velocity, bullet can kill a hog; but where I hunt, getting that bullet from muzzle to hog, without touching something else, is sometimes VERY hard.
Hence, my choice is a .308 for shots beyond about 50 yards while I use a large bore pistol (.45 Colt or .44 S&W Special) for closer shots. However, I have killed them with a .22 MAG.
Good luck with your hunting...