I dont know nothing about nothing in terms of African game, or even big game beyond deer. However, i have fired slugs and buck enough to have formed some opinions.
at very close range, buckshot IMO is devastating to thin skinned game, but, again IMO, with the average set-up, even 50 yards is really pushing the envelope.
While th ebore size of a slug is CRAZY overkill for deer, I think a lot of projectiles have been designed primarily with thin skinned (deer) in mind. The brenekke solids (maybe sabots too, I am not sure) seem to be an exception, among possibly others.
Obviously this post is basically redundant, and you can file it in the "yeah everyone knows that" file. A recent experience this saturday prompted me to post. Below...
I hunt mostly ML now, but when I use shotgun its either brenneke full bore or remington copper solids, since I get good-enough accuracy (relative) and excellent results with them. I witnessed someone shoot a 101 pound deer quartering towards, in the shoulder with a 12g remington copper solid. It hit the front shoulder and exited about 2 or 3" later on the same shoulder. BLew out a baseball sized hole. 70 yards. Deer fell but was most certainly not down and out. Just a huge urface wound. NOT the performance you expect in the least form a big hunk of solid copper. (Though it was the first time I havent had terrific results with one.)
OK, so the point of my post is, IMO (and IME?) I'd think LONG and HARD about which projectile you use when considering a 12g on any game larger and tougher than a deer.