I'd guess I'm the RB fan, but that's mostly personal as the second old BP rifle I got to shoot was a "rollie". (The first was a .577Snider Carbine...and that rifle does kick!)
Are a few positives to the RB, not the least of which is cleaning from the breech and having a clear view down the bore between shots, simple action that seems to keep on going forever, and simple stocking/bedding.
Disadvantages are there too. No set trigger (OK...can be done..but it's an expensive custom'smith job), firing pin can possibly stick forward (so you check when you roll that bolck back), and it isn't nearly as pretty as the Sharps.
The only down side of a Sharps is that some of the repros (and originals) break firing pins...that pin does have to turn a few corners before finding the primer, and each angle is a stress point. Less trouble with the repros.; the design is still angular, but the modern pins are stronger.
BUT...can buy solid original RB's for less than the price of the low-end repro. sharps, and a fine example for the same price as a top-level modern repro.(the price of an origianl Sharps, even in disgusting non-shooting condition, is a tad high). All I ask, as I shoot them, is that the old guns have a solid action and a good bore...prefer them to to be too colectable so that shooting them doesn't devalue them.