They both are great rifles, full of history and flair...I have both and also a rolling block...if I were to only have one rifle, it would be the rolling block, then the high wall, followed by the Sharps...the rolling block gives me a great prone platform without the lever and has a great lock time versus the Sharp...the high wall also has a better lock time versus the Sharp...
Maintenance and care would be best in the falling block and rolling block...the Sharps have more problems...whatever you get, you can't really go wrong with any of the great single-shot rifles...
Jack
BTW, mine are all originals and not replicas, so I can only speak for the real deal and not the newer designs...