Sevens hit it on the head. (Post # 24)
They were developed under completely different standards.
The .45 Colt started as a 'black powder' loading for a 'Plow handled' pistol. Further handicapped with 'balloon head cases' and some inferior weapons along the way (made in shops by unknown persons, using no or minimal metallurgical knowledge). Bores run from .451 to as much as .455 and more (don't jump on me, I'm not talking about any quality weapon here). Modern commercially loaded ammunition must be wimped down for some of these 100 year old black powder weapons.
The .44 magnum started out as a lengthened .44 Special, just so the rounds could be loaded up to greater potential in 'Modern' revolvers using modern steels and metallurgy techniques. About the only handicap being the design flaw of the Smith with the cylinder cut right on the thinnest point of the cylinder (over the chambers).
So we end up with two Kings. The Cowboy King, the true handgun of the old west. And the 'Dirty Harry King', of the 'modern' design.
Energy, velocities and size is transient. Someone can and will build something bigger, faster and more powerful. But, does that make it a King?
For me, revolvers are too slow to reload as a personal defense weapon. I want an auto loader. For target use and or hunting, give me a longer barreled revolver. I will not specify caliber as long as it starts with '4'.
Enjoy and be safe,