Although this is not always true, most of the Italian revolver reproductions have chambers that are smaller in diameter than the rifling grooves in the barrel.
While the chamber diameter is larger than the barrels bore the fired ball is not fully guided, relying on just the remaining bore to guide it.
This does not lead to great accuracy.
Yes, it is possible to have the chambers enlarged to solve this problem but that does mean spending more money to have an accurate gun.
The single shot on the other hand will rely on the ball size and the cloth patch thickness to create a tight fit with the bore and after determining the best ball/patch combination can produce some very accurate shooting.
That said, I must add that with either style of gun, the shooter is the weak link.
Shooting a pistol accurately is a challenging sport as the slightest misalignment of the sights, the slightest quiver of the hand or the slightest jerk of the trigger can change the point of aim and result in an errant shot.
The best way to avoid these conditions is to practice, practice, practice.
Whichever gun you decide to buy I hope you enjoy it as much as I enjoy mine.