I cast a vote for .44 Special and a 5.5-inch barrel. 240-250 grain lead SWC loaded to 950 fps. The clones will handle that pressure level, and it will equal or exceed the .45 Colt's ballistics fired from the more common
4.75-inch barrel with a 250-grain bullet, and won't give much up with the same loads fired from a 4.75-inch barrel.
The old Special is a marvelously accurate cartridge, and is easier to load for than the .45 due to less air space in the case...which is one of the reasons that I never really cared that much for the big Colt round...even though I own a couple of New Vaqueros chambered for it.
The .44 WCF or .44-40 is another one that shouldn't be underestimated. Thin brass makes it a little persnickety to load for...but with a 205-grain cast bullet, it can be loaded up to exceed the ballistics of the old .41 Magnum "police" round that consisted of a 210-grain LSWC at an advertised 970 fps...which actually didn't produce that level of velocity. Testing of several lots showed that it rarely hit more than about 900 or so. The .44-40 will break a thousand easily from a 5.5-inch barrel and nudge it from a 4.75 tube.