Some complain that the large side-hammer on the sharps gives a slower locktime and a bit of a shock that disturbs your perfect hold. I love my Gemmer Pedersoli. And you can't beat the "cache' " of the Sharps! Why hasn't anyone re-created the FREUND improvements to the Sharps?
Some say that the Hi-Wall was too late for the buffalo slaughter. It is, IMHO the best target rifle of the lot. (A fast, centre hung hammer, and an oblique falling block to seat slightly "proud" rounds.) Mine, after the barrel was bored to .38-55 by Ron Smith, is deadly!
The Roller has a lot going for it, while not, argueably, being the best in every aspect. (Tell that to the many armies that adopted the roller, and the target shooters of fame.) As I have a Pedersoli Sharps and a #3 Hi-Wall in .38-55, my next project is to get a long range target Remington. It is historically appropriate and has a great reputation on the target, and hunting, ranges of the 19th Century.
A toss-up. Take your pick!