I'd go with a Stainless Steel 1858 Remington replica for a few reasons:
(1) Ease of cleaning. Remove grips, dunk gun in HOT soapy water for a few minutes, scrub bbl and cyl(s) lightly, rinse in HOT water, air dry.
Stainless steel and black powder go together.
(2) The Rem has a notch rear sight milled in the frame not unlike many modern revolvers. Front sight can be dovetailed for windage, or bought that way. Either way, you're miles ahead of the Colt's rear sight, which is a damn small notch in the hammer face, visible (barely) only when cocked.
(3) Because of its full frame, the Rem is way stronger than the Colt, and won't shoot loose with full-power loads over time, as will the Colt. As for brass-framed Colts, they shoot loose even quicker than the steel framed ones.
(4) With practice and a little judicious rounding-off of a few sharp edges here and there, the Rem is VERY quickly reloaded with a spare cylinder, almost as fast as a modern revolver, and quicker than a SA Colt. The Colt Percussion pistols take a seeming eternity to reload, even with a spare cylinder.
Hint: Make SURE to buy the spare Cylinders for your Rem when purchasing the pistol, to ensure that they're from the same Mfr as the pistol, and so as to avoid size/fit problems later on.