Honestly, an in my experience, I believe its more shot placement and type of bullet used that is more important than caliber.. yes, that comes into play, but...

I have used .416's, 375"s, 338's, 300's all in Africa over 6 Safaries.. I don't remember ever having to shoot an animal more than once with the exception of my first trip there.. I had loaded some 180gr Accubonds in my 300RUM.. had them zipping along around 3370fps.. they were warm

loads...

Anyway, the old accubonds would not hold up to that velocity on game under 100 yards.. first animal shot was a waterbuck.. horrible penetration.. SO, I switched to my 416 Rem for the remainder of the trip for everything.. was shooting solids and 400GR A-Frames.. they did little to no damage even on the little stuff.. again, with the exception of a baboon that was about 180yards out running away.. he took one through the back.. about a silver dollar hole out his chest..

After that first trip I switched to Swift A-Frames.. loaded 180's for the 2nd trip.. worked fantastic..Loaded 200gr A-Frames the 2nd trop.. and have been using them in my 300RUM ever since for everything .. plains game, hippo, croc.. elk, deer, bears.. Also used 250's in my 338RUM.. 400fr's in my 416.. have had no issues and that is with close to 100 head of game harvested in Africa.. and more in N America...

As to Accubonds.. my experience shows they are a good bullet as long as MV is 3100fps or less.. have used them for most of my ibex,tur, and sheep hunts.. rifle is 280AI.. shooting 140GR Accubonds.. most shots have been 300 to 525yards.. all have been 1 shot kills.. with excellent bullet performance.. last once used with that rifle was actually an ibex in Turkey at 430 yards trotting through the timber.. he hit a clearing and I dumped him.. love that rifle..

Again, my point is, don't think any of those animals would have cared one way or another if they'd been hit with a 270 or 338.. all hit in the proper spot, all would have been just as dead..

Pic of Mr. Baboon..

IMG00137-20101030-2350 by A Hoffart, on Flickr