From a hunting perspective take two identical rifles, have one in 308 and one in 65 Creedmoor and I very much doubt whether you nor the game you are shooting will now the difference. A correctly constructed bullet is probably more important than the calibre.

And if the game will only be irritated by being shot with a 6.5 or 308, then you take out the 375 H&H or 470. And if its long range and needs really destroying then thats the job for the 338 Lapua, 50BMG or heavy artillery