If put in a mechanical rest, revolvers and autos of similar quality/precision have similar mechanical accuracy.
As badkarma pointed out, sight radius is one place you have to be fair in your comparison. A 4" revolver simply has more of it than a 4" auto on account of cylinder not being counted in barrel length. A .357 cylinder is gonna be at least 1.6" long.
Many people think of revolvers as being inherently more accurate due to the fixed barrel, but that isn't so. Yes, a sloppy lock up in an auto degrades mechanical accuracy. But so does poor alignment of cylinder and forcing cone in a revolver. In an auto, the bullet is pretty much perfectly aligned with the bore, save for tolerance between case and chamber wall. In a revolver, the bullet has to jump the free bore and hit the forcing cone. Depending on how tight the lock up is and how good the alignment is, you get anything from near perfect to deformed bullets with pieces being shaved off, even split forcing cones and frame damage.
Triggers are a mixed bag, of course. I have both autos and revolvers with single action pulls ranging from gritty and stiff to clean and pretty much breathe on it effort.
Also as badkarma mentioned, fit in the hand matters tremendously. I would say that autos fit me better for the most part, and that seems to be the majority of the shooting population. The grip angle and shape, the balance, trigger position. But for those who feel the revolver is more comfortable/natural in the hand, the wheelgun will likely shoot better for them.
In summary, I'd say it's a personal preference, both conscious and subconscious, as to which will be more accurate in your hands