I disagree completely with your friend, Jeremy, on the thin and flexible. Thin maybe, but you need the toughest steel that won't bend you can find. The blade should be 10-12 inches long. A 7 inch blade, after going through 2-3 inches of the shield, means you are only hitting one lung. I want more length, so I can strike through both lungs on one plunge.
A hog, even a sow, once it reaches 150-200 lbs, has a thick, almost impenetrable shield that is like a giant callous underneath their hide.Think of bacon, only its bacon you can bounce a hammer off of.
To kill a pig, you have to drive through 2 sometimes 3 inches of that stuff to get to the goodies..and if you strike a rib under that....well, you get where I am going with this.
I wouldn't necessarily use a Bowie Knife in the classic sense... I would want a full guard that extends above and below, like an elliptical guard, and I would want a sharpened like you ain't never sharpened anything before blade- with the top of the blade sharpened as well for about 1/4 of the length, tip toward the rear.
I'd want a no nonsense very tactile grip..nothing smooth or fancy, and a wrist tie to keep that thing in my posession after I stick the hog..you are probably going to need to get it at least twice.
Close quarters with 200 lbs of steel trashing its head around (make no mistake- a true wild hog only has fat on the outside layer...inside, he/she is all muscle and full of true grit!!!)