A .58 will drop anything that comes your way, big game hunter Val Forfett used a .58 back in 1973 to take an elephant, cape buffalo and a hippo...
He used a 610 grain "custom" minie-ball over 180 grains of FFFg...
The slug traveled lengthwise through a mature cape buffalo, possibly the toughest animal on the planet...
MM, The .58 is indeed a great caliber. I think anyone who disagrees is simply in denial. However, like any other caliber there is a "shootability" factor.
When we bring the recoil level of the .54 up to that of the .58...or, the level of the .58 down to that of the .54, it is IMHO the .54 that has a bit of an edge.
Bigger and faster will always be the winner no matter how we slice it, but how much of a good thing can we stand?
I shoot a Lyman 575213PH in my .58. This puppy weighs 565gr and has a thick skirt on the HB. The thick skirt requires a lot of powder to get "bump-up", and good engraving required for top accuracy (130gr FFG, or 110gr FFFg). This is NOT a load to shoot from the bench for fine tuning hunting load accuracy....it is absolute dynamite for those who can control it off sticks, or standing free-hand.
On the other hand, the .54 with a .485gr Lee OS Conical, with about the same powder charges, can be "fined tuned" from the bench, albeit it is not a fun thing to do either.
So, the best caliber would, IMO, be that caliber which you can shoot best with it's heaviest loads, and that could well be a .50, or a .45 cal.
BIG, heavy calibers that don't hit their mark are useless.
BIG, heavy calibers that do hit their mark are priceless.
Every single person must look at what "he" can do with "what".
Age also has a way of making those afflicted look for itty-biity calibers that can perform miracles...and that's where I'm at if the truth be known. Those big bruisers have knocked the snot out of me for about as long as I'm willing to put up with.
Just my thoughts on this never ending, but very worthwhile discussion.
Respectfully, Russ