This reminds me of the old Greek argument of how many spirits can dance on the head of a pin?
In all seriousness, some points to ponder.
The 2 grand daddies of the pack, the 300 H&H and the old 30 Newton, were very balanced rounds, so is the 300 wm and 308 norma. The new short mags and big case boomers make their magic at some very stiff pressures, with the latest modern powders. If you loaded the all to the same pressure level, you'de be suprised how level the field gets. There is no free lunch, the laws of physics still apply. Not to mention how some bullets react when driven hard.
Some points already mentioned, ammo availability is a very good one. Case in point: wife & I went out in southern sask last fall, me with a 308 win, her with a 7-08 rem. She made the mistake of putting all of her 20 rounds into her coveralls. After one bushside stop, 1/2 hr down the road, out pops Bambie's daddie and the girls. Wife reaches for ammo, it's gone. Now try to find 7-08 in the middle of buttf*ck sask! Lots of 308, 06, 300wm, 270, 243, 303, the usual basics. But no 7-08.

Same situation some years back in Saskatoon. Sitting in hotel talking to some US hunters on the way to a camp. One fellow had a beautiful Weatherby, 300-378 jobbie. Problem was, ammo got shipped seperate from gun, and lord knows where it went??

That beautiful gun became a large paperweight when he couldn't find any ammo for it.

Something to be said for a standard caliber.