Rkensparc:
The practical hunting range for the .45-70, .45-90, etc. is limited by the iron sights you'll likely be using on these rifles and your own range estimating abilities in the field. For most of us, 150 yards is getting there, and with traditional BP loadings, you'll want to know that range pretty close. For example, the Lyman 457125 520-grain bullet at 1300 needs to be almost a foot high at 100 yards to be on at 200, according to the tables in the Garbe and Venturino's SPG Reloading Primer. Smokeless will flatten things out some, but not as much as you might think. These guns can of course be accurate out to 1,000 yards, but that's with a lasered shooting range and a notebook full of sight settings.
I wouldn't go beyond .45-90 if I was planning to shoot a lot of smokeless, as excess cartridge capacity starts to be an issue when using smokeless in the old BP cases. With black, I would not be concerned with recoil in any of the cases you mentioned from a hunting standpoint. But you won't find many shooters  using .45-110s in target matches, as a string of 30 or 40 rounds from the prone position makes recoil an issue.
Many consider the Highwall with its small, central hammer and fast lock time the finest of the old BP single designs, and it  is probably the strongest from a smokeless standpoint. However, from a historical standpoint only a few of the earliest Browning-made versions of this rifle likely saw any use at all in the buffalo harvest, as the rifle came out after the herds had nearly vanished. The Sharps, Remington rolling-block, Ballard and Trapdoor Springfields did most of the work on the buffalo, so if the history is important to you, get the Sharps rather than the Highwall. I like the Sharps myself.
I'm not aware of any Spanish Highwall or Sharps copies, but among the Italian makers, Uberti builds the Highwalls and gets pretty good marks. For an Italian Sharps, go with Pedersoli and avoid all others (IAB,Taylor's etc.). Pedersoli makes the best of the Sharps imports by a long sight, and their barrels are simply excellent.
Good luck with your choice.