RE: Importance of Barrel Length
I don't think that barrel length has anything to do with the intrinsic accuracy of the pistol, but it can certainly effect the practical accuracy. What I mean is that two similar guns, say a Springfield XD Service (4"bbl) vs the XD Compact (3"bbl), that are made to similar tolerances would likely show similar levels of accuracy when shot from a machine rest under controlled conditions. However, the 4" service model has a longer bbl and therefore a longer slide, which increases the mass (and inertia) making the pistol easier to hold steady, and will have a longer sight radius making it easier to aim precisely. Overall, the longer the barrel and sight radius, the easier the pistol will be to shoot accurately. Of course, there is a point where more barrel becomes a problem because the pistol becomes front heavy and doesn't point naturally, but this usually isn't a problem with any but the biggest revolvers.
Mike