Ullr,
Shooting the 45colt out of a 454 casull is okay, but extensive usage that way might cause erosion in the throat, it happens here and there with .38's used in .357's. Human nature what it is, 454 is expensive and you may find yourself shooting more 45colt instead. If you are looking for power, get the 454. Don't bother trying to hot load the 45colt, the brass can't take it very long. On the other hand, the 45colt is a very good round. There are more different loads available for it now due to SASS shooting and if you do any reloading or casting, there are a lot of options especially with cast bullets.
Wallynut