If I was setting out to build a rifle, I probably woulnd't use a Uberti. Considering the total cost of a gun, the difference in price for a premium barrel won't be that much. But will the extra price result in "better" shooting? Nah, I sincerely doubt it. As already noted, Uberti's have a rep for really good accuracy.
But the premium barrel would let you get into swamped or tapered barrels, which dramatically affect the handling and balance of a gun. Maybe that makes it "more accurate" because you simply shoot better with it, no matter what it does on the bench.
By the same token, if looking at an existing rifle with an untapered barrel, where are the bonuses for a custom barrel if it doesn't shoot any better than the Uberti? It boils down to a question of the fit, feel and finish of the gun in my mind. If there's a price penalty for being a Uberti, it would be the cost difference between new Uberti and premium barrels and no more.
If the gun is well made, appeals to you, and especially balances well for good shooting, buy it and enjoy. You might be able to knock off $50 or $75 or even $100 because it's Uberti and not a premium, but don't let that sucker slip between your fingers.