I've always looked at anything under .400" as a medium bore, anything over as a big bore, and anything over a .458" as a stopper. That's just how it works in my head, and I'm okay with that not matching the common perspective as .458" being the starting point for big bores and .500" being a minimum for a real stopping rifle. I'm no stranger to being wrong, according to my wife.
I've owned a few big bores (in the common vernacular), and hunted with a .458 Win Mag for a while. It's a devastating bear gun! When you're hunting over baits and have the ability to dictate range, the trajectory becomes irrelevant. Energy dump is everything, and a 510gr soft point was *quite* authoritative. If I was going to do another, as a handloader I would probably choose a Lott. But maybe not, the Win Mag is a sledgehammer. I might even have dies still, and have more that one long action, Magnum bolt face action kicking around.
I just see more utility in the .416s, most of those same actions will eat .416 Rem Mag which is no slouch and would probably be my Africa choice if it ever rained Lotto 649 at my house. The others will eat the lesser .416 Ruger as well (the princess of the .416s).