I think you are confusing cap & ball replicas with Single Action Army replicas. The Uberti short arbor issue is a cap & ball revolver issue, nothing to do with the SAA.
My opinion is that Uberti used to be better than Pietta, but Pietta has made great progress, to the point of getting ahead of Uberti.
BTW the C&B arbor issue is the reason why I recently bought the Pietta 1851. The timing was good out of the box, everything feels solid and the revolver functions perfectly. I have also owned two Pietta 1858s and those were perfect. I only had problems with my 1873 clone, but will buy another one and post a review once I get it.
Indeed Pietta has taken liberties with C&B designs for some models while Uberti has remained faithful to the originals. For C&B, from a historical standpoint, I'd stick with Uberti, but to shoot, I'd say Pietta.
Back to the SAA, what eliminated Uberti for me is their new hammer safety. I don't think Pietta has anything like that. They sure didn't on the one I got a few years ago, somewhere around 2014, maybe 2015. Darn, that's already 8-9 years ago!
Gil.