From my unbiased experience and owning several of both, for what it's worth.....
The Uberti guns are fitted and finished better, but will have a short arbor for those concerned about this.
4 out of 6 of my Piettas developed timing issues after several hundred rounds to the point where at half ****, or when the hammer is moved just past half ****, the bolt moves up out of the cutout. I'm currently working on them to see if polishing up the interface of the bolt leg and cam may fix it, or maybe these guns need to be thoroughly detail cleaned every time you fire them because they did not do this when new. Or if the bolt leg and cam became worn this quickly. I ordered 2 new bolts from Taylor's to see if I may have bad or soft bolts with legs that are too short. I even ordered a Uberti bolt to see if maybe I can fit it, just to try it. If I can fix this, they'll go back to being good shooters again . Hopefully they just need some "fluff and buff" to the internals.
I have admittedly fired 1000s of rounds through my Uberti 1851 Navy without detail cleaning it and it hasn't developed this issue
My Piettas are very accurate and solid guns otherwise, they still function with this issue but perhaps the recent run of them have bad cam fitting or soft bolts. All of my 4 .36 Navy brassers have at least 300 rounds through them which isn't a lot. One of them had a loading lever that was too short and rattled around. For $220-250 for a Pietta Navy I don't expect perfection but they may need some work or tweaking.
The brand new Pietta Colt Navies have a higher front sight pin regulated to 25 yards. My new 2022 .44 Navy is dead nuts at 25
My one Uberti Walker developed a little slop in the fit of the barrel locator pins , after a few range sessions with 50 grain charges. These definitely need the short arbor fixed.
I honestly feel with post-Pandemic production it's a toss up. If I were buying one myself I'd get the Uberti.
All of my 6 Piettas are brasser Navies, that I bought to use as range blasters and to tinker around with.