I'll take the bait. I think even a highly subjective and biased "BEST" has to be put in context.

First you have to define best, and depending on what is your definition or theory you can contrive a reasonable argument for almost any cartridge. And probably based on that same definition, another could come back with a new design or propose something already out there is better. It never ends and gets pretty pointless after a while. IMHO.

If I want a 40 cal CZ550, I think I could make a good argument the 416 Rigby was better. if another wanted to build one size rifle for all hunting from lowest cost, they might propose the Ruger was better. If I had an M70, I might propose a 404 was best, while Winchester might argue the 416 rem was better and you would want the Ruger.

What counts for you? A 100 years of success in the field? Availability or fit in a certain gun? Brass and bullet availability? Shortest possible OAL? No belt? Sharp shoulder? Good body taper & gentle shoulder for feeding? Burning the least amount of powder to hit a certain magic fps number? Or maximum versatile in what powders will deliver. Does it have to reloadable in some African country that only has access to limited powders? Do you want to be able too use cheap bulk powder? Do you favor low pressure or hi velocity? What velocity is optimum? Large variety of factory loads? Ammo available anywhere in the world?

Define your requirements and make your choice ... Or ... Pick you favorite first and contrive a set of conditions that justify that choice. Either way same game.

I'll generally favor one of the old classics. In .45 there is really none for a magazine rifle. That leaves the Lott as best and most popular in class. By my definition of best.

The somewhat insidious problem with what Ruger has done is they are diluting an already very thin market. You can find 375H&H ammo for reasonable. So far. If we had one good standard 40, you probably could do the same there. As much as I think Winchester screwed up with the 458WM, in the old days there was a fair shot you might find 458 ammo in a well stocked shop and there was some price competition. Today we are lucky if even one company will load ammo for our pet big bore and be prepared to get reamed out if its anyone but Hornady.