I'll speak from the standpoint of a butcher and a meat cutter that has done a lot of hunting, including Africa.
First, let's look at butchering, as that seems to be the main interest in this article. The most important thing in a knife is the handle, one that is comfortable to your hand. If the handle is comfortable to you, you're better than half way home. Now the blade. For butchering, i.e. removing the hide then evicerating, think about how much blade you actually use, the amount actually cutting. A skilled butcher might use 3" of the blade on some, but not all cuts, so much more blade than that is wasted. The size of the critter means little to nothing (though I haven't worked on an elephant or a whale).
Skinning knives have a significantly swept curved blade, no sharp point, to maximize size of cut and control. Most of the cutting is on the "belly" of the curve. While I like folding knives for carrying while hunting, folders aren't conducive to a good skinning blade. Consequently, I generally carry a fixed blade skinner in my pack. A skinning knife also works very well for removing the lower legs if you know where to do it, and the knife also works well for opening the body cavity after the skinning is complete. Also, I should point out that contrary to what most have said, one does NOT want a super sharp knife when skinning. Sharp, yes, but not shaving sharp. That will only lead to hide cuts, which generally aren't a concern on game (unless you want the hide or are getting a mount), but one will find a medium sharp skinner to work much better. Oftentimes in the plant we have to take the knives of eager new or young butchers and actually dull them a bit. You don't want burrs or knicks, but you don't want it razor sharp, either.
Now the butchering is done and we come to the meat cutting. Again, the most important part is a comfortable handle. The majority of the cutting is done at home, but often it is necessary to do some priliminary work in the field, i.e. boning out the critter for packing out. The wide sweeping curve of the skinner is not your friend here. You need a somewhat longer, straighter blade, and now you do want that mother sharp. It cannot be too sharp. To keep it that way, you obviously want to avoid directly hitting bone. Fillet the meat off the bones, don't cut into them. A steel is a great aid in keeping a sharp knife sharp during use, indeed, that's what it's for.
As to blade length, again, consider how much blade is actually working. You may want a bit of length to reach in deeper on some cuts, but never will a blade longer than 6" be anything but a hinderance (we're not talking slicing steaks here). So, while out hunting do we need two knives--one for butchering and one for cutting/boning? Ideally, yes, but in reallity one can get by quite adequately with a good skinner if you don't choose to pack two. If you only have one, a skinner would be much preferred over a boning knife (the proper name of these longer straighter blade knives). That Gerber that was pictured by Mr McGunner is a real good compromise (prividing that the handle is comfortable to you). What is called a legging knife in the trade is a real nice compromise also, and indeed, resembles the illustrated Gerber quite a bit.
The relatively small folding bone saws (Gerber) are excellent for splitting pelvis and brisket, and worth carrying in my opinion. I think it's industrial strength dumb to not carry a small stone for touch-ups.
Cheers guys, and good luck to you. Hope you need those knives!
Oh, as to Africa. Fact is, as a hunter there, that's about all you are. You don't do the butchering or the meat cutting. If you did, the same knives would be called for, elephant being one I can't talk to, though.