There's probably not much difference between the 44 Magnum loads that you reference and the really powerful stuff you can load with the 45 Colt. The Colt is a step up, though. It's not a quantum leap up, but it is higher on the food chain.

Really, if you are going to be serious about this you must handload.

Now, cartridges like the 475 L and 500 JRH, to give a couple of examples, are demonstrably more powerful than any 44 load. There's no getting around it. And though I do not have the experience of some of the others with regard to killing game with the big boomers, I have plenty of experience shooting them and loading for them.

Back to the 44 vs. 45 argument: You may never need the extra little bit of performance that a stout 45 Colt can deliver; certainly not while hunting whitetails. But, there is something to be said for a larger diameter bullet with a larger meplat. So again, there is a performance difference between the 44 Mag and the 45 Colt but you will never realize it while hunting deer. And for that application, your 44 Mag is as good as the 500 S&W that you got rid of a while back.

Now, start loading for that thing!

Well, when you can find components, that is.