the rifling is different in UBERTI and COLT, clockwise in one, anticlockwise in the other. The chambers are bigger in UBERTI, around 11,62 mm versus less than 11,60 in the COLT. The bore is 450" in Uberti, and 451/452" in colt.
That rifling in Ubertis seems more thought for smokeless powder as it is not as deep and crisp as the original first generation Colts, with a wonderful rifling that allows optimum results when shooting pure lead and BP.
the steel is very good. The Piettas use softer steel. I have engraved the 3 makers. The easiest to engrave was the Pietta, the modern Colts, were the hardest, with the more refined steel, with clean brigth burrs at every cut.
the finish in UBERTI is also away from the original XIX century Colts, with a poorly made fake case hardening and nitre blueing with very forgettable sanding and polishing in parts. The original Colts were heat blued, and some army issue revolvers, were even rust blued in military arsenals and had a superb finish.
in my opinion most Pietta/Uberti/Chiappa replicas are a step behind the originals when it comes to accuracy performance. It is just personal experience, specially, with muzzleladings, but it also applies to SAA´s.
Everytime I shoot an original with BP, I realise how good guns were in their time for just one reason:
most, with average condition bores, shoot like true champs without much effort!
Armi San Marco made a great replica long ago, with a beautiful finish, that was a great shooter with anything, black powder and smokeless. I was fool enough to sell mine many years ago.
Piettas are nicer guns when it comes to finish, though nothing comparable to the original Colts. I have no experience shooting them. The frame seems to be either a casting or maybe just fully CNC machined from steel block. The Uberti and Colts are forged frame guns.
Probably Pietta is the best buy today, with a beautiful finish made with more attention to detail than Uberti, with better sanding, polishing and case harden...and in general, , well made guns, and affordable. That is probably one of the reasons why they are sold in larger quantities than the Ubertis.
all the best.