I personaly have two of my own knives dedicated strictly to hogs. One is a custom made "bleeder" that I am feild testing, the other is an old "Air force issue, pilot survival knife" that I purchased off of e-bay, and I have been real happy with it, because my hand size, it is very comfortable and suites me well. I am not a big fan of a huge knife, a 6" blade does everything I need it to do, amnd it alot easier handling in a tuff situation where I may be haveing to work in a realy cramped space. My husband uses the old Bayonets and swears that those are the best.
Some guys will use spears and it is all about "personal preference". I like the smaller because we do more hog removal (4 days a week, in the farming season) then guiding, and do all our dispatching up close and personal. In some cases, when catching the hog, the brush may be so dense that We will be on our belly's, crawling into a real tight spot with our dogs hold the hog the best that they can. In those cases a spear or a gun would be too dangerous for the dogs, you have very little room to manuveaure, and will actualy have to slide your arm in between the dog and hog to position your weapon in the kill zone.
When using any weapon while having a dog hold the hog, you have to calculate carefully but stay committed to objective. The smaller the hog the dogs can usualy hold it in one spot, but when a hog gets up arouhd 100 lbs or more, thy are incredible strong and because the use there neck as their main muscle for rooting around, it is nothing for them to be able to lift several dogs or a person completly off the ground in a split second. That is why legging the hog first helps for safety of hunter and dogs, it is just a good practice to get into too. I have been holding a back leg of a good sized hog (not a monster) and have two dogs pulling it's head down and the hog is still moving dragging us along, and I m experienced at this, so when I say they are strong and dangerous, I am not hyping it up. But back to the spear in the ideal situation a spear is a GREAT choice of weapon, but in a close tight situation it may be harder and longr to get the clear shot at the kill zone, because either a dog is in the way or tight quarter may not allow you to position the spear at the proper angle to make a clean fast kill. At that point your guide would have to make the situation right, by manuvering the hog around to get a clear opertunity, or by going ahead and pulling a knife to make for simpler kill. You just never know when you are hunting free range hogs where you may end up. I would saythat if youwanted to use your spear, bring both your knife and spear, and if the oppertunity presents itself you could take one with your spear. Then maybe you could try both and see what you prefer on two seperate hogs.
Just to give you another example, in hot weather the hogs will tend to go into water, plenty of times we are waste deep in a creek, a hog is a wonderfull swimmer and has an advantage over all. holding the back leg and the hog is still swimming in the front in but the kill zone is submersed. I have to run my hand down a hogs should to feel for acurate spot, and then with my knife in other hand I have to guid it to dispatch the hog. All of this has to happen quickly, I would problay stick myself with a spear in that situation.
Hogs are wonderful animal to hunt, their intellegence is incredible, for as ugly as they are the have incredible survival skills, and they learn and are capable of adapting anything. So this also makes them a tricky advesary when to trying to hunt them. So when you starting hunting hogs you can easily get addicted to it, very exciting and never the same twice. Never get bored because you will never expect repetition. Even when you don't catch anything, a bad day in the woods is still better than a good day at work!