Please forgive my ignorance. Am considering one of these calibers. What would the difference be. The case seems to be similar in size. Is their a difference in speed, trajectory? 44Rem mag or 45 colt? Thanks for any help.

You need to read this:
http://www.sixgunner.com/linebaugh/dissolving.htm

Somethig to watch out for, on the 45 LC many guns are chambered for 410 shotgun also. This usually ruin the accuracy shooting 45 LC's

On paper, the 45 Colt does have some edge over the 44 Magnum. In the real world neither you nor anything you shoot with either one is going to know the diference. But you must handload to get the most out of the 45 Colt. Too many old guns and copies out there of the Colt SAA for any ammo maker to turn out hot stuff. I imagine Corbon does, but the 44 Mag is far more practical for the non handloader. I have a 44 Magnum NEF Handi Rifle, and absolutely love it. I wouldn't trade it for any advantage the 45 Colt offers.