The results of a 243 Win, one Barnes TSX, my 9 year old son, imperfect but adequate shot placement, and 40 yards of follow-up.
I'd be the first to admit that more rifle is less limiting, which I why I use a 30-06. I love the romance and intrigue of Africa, but the oft-repeated nonsense about the bulletproof nature of its animals is not part of the lore that I find interesting. Put a bullet through an important part of the circulatory system and an animal will die, full stop. Good bullet construction and heavier hitting rifles make that easier to do. A person has to know what he, his rifle, and his bullet together are capable of and work within those limits.
I've no issue with any man's choice of rifle as long as he knows what he can and cannot do with it and works within those limits. I do find it unfortunate that "use enough gun" has probably done more harm than good in that many people show up to Africa with more gun than they can shoot well. Ask 100 experienced PHs if they think a 308 is adequate for plains game and I doubt you'll find a dozen who think it is not. Ask 100 PHs if they think a 375 is better IF THE PERSON CAN SHOOT IT AS WELL as his 308 and I doubt you'll find a dozen who think it is not.
Rifle choice is a balancing act. If you have the ability to shoot a bigger rifle well, that is in my mind the best choice. If you have the ability to shoot a 30-06 well, that is a perfectly adequate choice. If you have the ability to shoot a 243 well, you better learn to be patient and choose shots wisely, for it is not forgiving.