I tend to err on the large side. There is an argument here about being able to fully penetrate the chest cavity with a non-obstructed, broadside shot. I look at it a bit differently.

A big game hunt, whether guided or "on you own" represents a large investment of time, energy, and money. I don't want to have to wait on the perfect broadside shot that may or may never present itself. I prefer using the largest caliber possible as long as it can be shot well without flinch. To me that means practice and nothing more. I want to be able to place my shot from what ever angle is presented to me and reach the vital organs.

What does that mean in terms of caliber and game? Here are few examples: Please note these are the calibers I own so any within the same power capabilities are implied as well.

Whitetail deer: 270 Win, 7mm Mag., or 300H&H.

Elk: 300H&H or 340 Weatherby Mag.

Moose: 340 Weatherby Mag. or 375H&H.

Brown Bear: 375H&H or 416 Rigby.

Leopard: 300H&H

Lion: 375H&H or 416 Rigby.

Buffalo: 375H&H, 416 Rigby, 500NE

Elephant: 416 Rigby or 500NE

Plains game: 300H&H or 340 WBY.

I normally hunt Dangerous Game when in Africa so am constrained by the limits of 2 rifles on the trip. I've used the 375H&H on animals as small as Steinbuck using a solid without undue damage to the pelt. I fail to see any real disadvantage to being overgunned especially when matching the bullet to the game to prevent damage. I can't say the opposite however as I do believe it possible to attempt to take large tough game with too small a weapon. Not to say that the smaller weapon will not kill the animal, but it may not do so in a timely manner leading to the animal escaping to die a slow and painful death. I just don't understand the fascination with experimenting with how small can you go and still get the job done.