My preference is the Ubertis, because they hide all the trivial stampings under the barrel and covered by the loading lever...petty, I know. Other than that...?
My first Uberti was bought from a friend, who had it from new. He'd cut down the barrel to about six and a half or seven inches (I need to measure this) and filed down the foresight. The Pietta is older and unknown history. At some point, the link between the loading lever and rammer has been bent, which makes loading a pain. Also, the chambers seem to be tighter than the Uberti. As far as I can tell it's standard, with a full length barrel and original foresight.
As far as shooting goes, it's pretty much a wash.
The plan now is to have the "new" gun cut to match the first one. Then have a play around with the Pietta. I really like the idea of a stainless Remington Bulldog similar to Mike Beliveau's. (Hey...is he Bottom Dealing Mike on here?) Just need to find a company who can post a Howell quick release catch to the UK.