Completely fair question.
Let me take a cartridges to compare.
300 s.i/Sherman mag w/215 berger
82 grs H1000 yields 3050 fps
My 300 win mag
77 grs H1000 yields 2905 fps
All with the same length barrel. At what distance would the terminal effects be noticeably different?
The issue in comparing powder amounts is the difference in burn rates. Its a bit like comparing gas mileage of a V6 turbo vs a big block V8 - with both having roughly the same HP.
Faster powders use less grains, but have more"punch". Slower powders use more grains, but have more "push".
Every aspect of any cartridge design is a compromise in some way. SA Vs LA is a non argument for me. When I rack another shell, an extra 1" of bolt movement hasn't ever been noticed. And sometimes the added weight of the LA is welcomed due the recoil generated. There are LA cartridges that feed better than SA (300 WM vs 300 WSM). The short mags are sexier cartridges by far

Shorter/fatter cartridges tend to have an efficiency advantage of ~5-8%. Is it worth buying a semi niche cartridge to get this benefit? Only the buyer can decide.
The laws of physics haven't changed. Pressure moves bullets. To generate the same velocity, a faster powder needs to have a higher peak pressure and a slower powder needs to have a longer duration over 15k psi. There's no free lunch and there's no replacement for powder capacity.
Tdot- I know you shoot one of the Sherman cartridges. So, for you it made sense. As a fellow handloader, I rarely see any "real world" benefit from new cartridges. The biggest benefit for most people I've worked with is a high quality trigger and barrel. At the distance most deer are killed - arguing over SA vs LA or cartridge efficiency, is purely academic.
The risk with the Sherman cartridges is, where will they be in 10 years? Even big companies fail (30 TC, some of the rsaum + wsm didn't make it either). Will there ever be loaded ammo? We live in a great country that affords is these discussions.
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