Same one for hunting everything in North America: .270 Win. It's darn near as good as the .280 Rem, but I don't own one of those. Were I to pick the best cartridge for all North American big game hunting, it'd be the .280 Rem. What separates it from the .270 Win is the legendary 175 grain bullet the .280 Rem fires. The .284 caliber 175 grain bullet has legendary penetrative ability. But the 150 grain .270 Win Partition ain't too far behind. The '06 is right up there with the .280 Rem.
BTW, any of these three will kill just as dead as ANY mega-magnum. All you gotta do is put bullets where they need to go.
How long would anyone suppose an elk could like without topside oxygenated blood flow? Maybe 30 seconds? A minute, tops? Does it matter what destroys an elk's heart? Or does importance lie in destroying it?