No.

At equal pressures and the same bullets, the .458 will always outspeed the .45-70.

With a long barrelled rifle and max pressures, I have read of 2000 fps being reached with very heavy loads in the .45-70.

John Taylor considered his Martini-Henry .577/.450 adequate for lion, that with much lower velocities than max pressure modern .45-70 loads. He shot 480 grain bullets at, I suspect, less than 1400 fps. He also considered some of the BP Express guns adequate for lion and tiger, rounds that, again the modern .45-70 can beat. But did Taylor consider the .577/.450 adequate for all conditions for DG? No, and remember, most professionals don't consider the .375 totally adequate for all conditions, either. Maybe Duggaboy does, but I don't think so.

It is true I do not have African DG experience. I do have years of experience with the .30-06, .375 and .45-70. I am a life member of the KwaZulu/Natal Game Conservation Association, joined when I lived in RSA in the '80's, where, since the topic seems to involve sired children, my son was born. I have travelled extensively in southern, eastern and Central Africa, the latter in then-Zaļre. The folks I lived with there began control hunting of elephant first for the Belgian authorities and then Congo/L and then Zaļre. They shot many hundreds of elephant over 30-something years and of buffalo I have no idea. Lots.

Their first rifle was a .375 and later they added a .458. I learned alot about the .375 from them, specifically its limitations with the bullets that were then available. Their experience was the experience of success and failure. They had generally positive but mixed opinions of the .375 and passed those on to me. A super cartridge, to be sure, but no .458.

I have never shot a test of a 500 grain FMJ from a .45-70 running at an easy 1550 fps, but I am reasonably certain such a shot will equal the depth of penetration of a 300 grain .375 FMJ. Top bullets in the .375 shoot about as well as tops from the .45-70.

I do not believe in sticking with past prejudices if proof speaks otherwise. That "proof" I am finding more and more in legitimate tests {on game and otherwise} of heavy .45-70 loads, published more and more from a variety of sources. My experience agrees.

To equate the heavy-loaded .45-70 with the .30-06 is ludicrous. I might add that Daryl's bringing up of the .450 Alaskan is appropriate. I did an extensive interview with Harold Johnson about a year before his death and he was 100% clear in his assessment of the .450 Alaskan and the "Fifty" as he called the .50 Alaskan. In fact, he told me in effect, if he had had access to the Marlin .45-70, he might not have gone to the trouble of the .450. And he considered his .450 light years more powerful than the .30-06, THE CALIBER HE HUNG UP FOR THE .450.

Regardless, though, to be clear, to equate the .45-70 with the .458 is also silly.

But the .375? Johnson was adamant that his .450 was far superior ot it on big bear.

So we have the .375, a legitimate and classic medium shooting relatively light bullets at moderate-to-high velocity. Yes, I believe, if any comparisons can be made, one legitimate one is the rough similarity of killing power of a heavy-loaded .45-70 and the .375, at short range, with best bullets fired in each one. In some cases the .45-70 may indeed be superior, but as to versatility, there is no question, the .375 beats it hands down.

{post edited after I checked my Johnson notes}