Accuracy from a purely mechanical viewpoint, a short fat barrel is more accurate than a longer thin barrel. Longer barrel will give you more velocity, but will vibrate more. As you are not extending the sight radius, which would aid in accuracy I do not see a reason for doing so.
I am considering having a 6 inch barrel put on one of my TS in 357 Sig, but the goal is not better accuracy it is hopefully another 100 fps. on a 147gr bullet. The gun is for pig hunting.
Just my thoughts. Good luck on your project. Really miss my 85.
JW