The 1858, I like the Looks, feel/balance, reliabiltiy, structure, i.e. sights and frame along with chamber capacity/ease of changing cylinders. Not that it's needed but nice to have a choice. It's low maintenance,most are good to go right outta the box. Accuracy has also been a plus for me. Would like to get a new Euroarms 1858 cause I like the dimensions and authenticity in size of the ASP I have. Closer chamber to barrel size also. I have always been a Pietta fan and always will be...I equally like the Uberti models. I have one of each and like um all, but I think the Uberti 1858 chambers take a .454" ball, Pietta take .452" same with ASP. I guess the only thing I can say I don't like is not having more of them.
The 1860, I can't explain it any better than this;
The Lines of the 1860 are perfect it's a piece of art. I looks great has excellant balance and pointablitiy. It just plain feels good in my hand and I have trouble putting it down when handling it. Some Colts need a little pampering probly the replicas more than the originals..but they all needed fine tuning and maintenance. When they get broke in and loosen up a little it's to be expected...and plenty of info and knowledgable people in here to help with questions. Like shims, wedges, chamber diameters, Bores, sights...the list goes on. I for one am pleased with my Pietta 1860 shoots great and very accurate because it's in proper working order/tuned and all the bugs worked out, this ones 10 years old and tight as a drum. Plus I can shoot...LoL!
Colts have more things that can loosen up on them like arbor lock pin, arbor to barrel assy. to wedge...but you gotta admit the are a thing of Beauty and ya gotta love um.
My favorite on Both Models would be:
6)Armi San Marco
But all said, I'd take an 1858 Remmington if I had to choose one.