RE: 45 or 50 cal
I too would go with the .50cal. There are a lot more load possibilities available for them. Plus, as Tikka mentioned, local regulations can become overly restrictive in the smaller caliber. For instance, some states list the minimum size bullet for muzzloading as .44 or .45cal. This rule eliminates the use of all sabots in a .45cal gun - meaning you would be restrited to using conicals or the Power Belts (which ARE an excellent choice regardless of the rules).
"Every moving thing that liveth, I give unto you as meat" (Gen 9:3)
Trust God..........but keep your powder dry!