Hi, I have used a 500 nitro express on Cape Buffalo, also Australian Buff, plus I have used a 460 Weatherby on massive Scrub Bulls, and a 505 Gibbs on Australian Buff.
Nothing with full loads and a soft point hits as hard as a 460 Weatherby, very closely followed by a 505 Gibbs. The 500 Nitro was my least favourite.
So through doing a lot of real hunting with my 460 (approximately 250 rounds) over 30 years. the big Weatherby wins Hands Down.
An interesting comparison, I shot a Massive Scrub Bull with my 500, and it took 5 very well placed shots, to put him down, the last one at 20 yds as he was about to charge, with the 460 same size animals(6 big bulls) shoulder shot, and dropped instantly, my Gibbs very similar, just not as devastating.