Uberti, makes a slightly better model, but it is easier to get parts and spare cylinders for the Pietta.
The cap and ball cylinder is legal for some hunting in PA, such as groundhogs and coyotes.
The 45 conversion to centerfire cartridges is legal for deer and bear in most of the state. But the conversion cylinders are not made for hot loads.
The cap and ball cylinder models were legal to hunt deer 25 years ago in PA. Until 40 years ago, Remington labeled it's percussion caps as centerfire. As did Winchester, UMC, etc. Whether a percussion cap model comes under the definition of center fire now is subject to no small debate.
Uberti is better. However, Pietta Remmies have been on sale at Cabelas recently for about $200 with shipping and an Uberti will run almost double that. I own both Uberti and Pietta products and I'd say the latest Pietta products are about 95% when compared to an Uberti.
If you can find a ruger old army in like new condition (out of production) it is better than both of those Italian brands, but sadly no where near traditional. Parts for the Ruger are getting rare and expensive.
Conversion systems come in five shot and six shot. Go to Taylor's and look on-line at their six shot conversion cylinders. Note how very little cylinder wall there is between the cylinder exterior and the chamber wall. I said no hot loads and you can see why. Then google Kirst converter cylinders. There may be another maker now. I know there is a 22RF converter for the 1858's.