An interesting question but flawed. My experiences with the 3 italian 1873/76 rifles that I have purchased new is that they were broken when I got them. The first one was a 30 in bbl 73 that had a absolutely useless bbl. It spent a year at the Chappy importer in Texas while a replacement bbl came from italy. The second was a RCMP 76 carbine with toggle issues that was a active post here last year. The last was a 73 carbine that has soft screws and springs replaced to get right. All 3 took a substantial amount of effort to get to where they should have been when they left the factory, they do work now but are not my match guns. My 3 Marlins I've owned came from the factory 100% without any problems. The 1894s had one piece firing pins installed and after a lot of shooting my main match rifle developed the Marlin jam but I repaired it and it's still my match favorite. With my experience, I would have to say that your question needs to be -after repairs and competition upgrades- how durable are 1873s?
If you are talking Chapparals it is well known they were and remain junk. Ubertis, the new Miroku Winchester and original Winchesters are completely different animals. 73s are the top gun for high levels of competition. If they weren't reliable they would not be the overwhelming facovorite CAS rifle.