The reason it's more accurate is because it looks like a Python, sorta, and everyone knows the Python is the most accurate .357 mag ever produced...well...up to the production of the S&W 686, at least.
In all fairness, Colt did hold their production guns to higher tolerances than S&W, so it was easier to get a Smith that didn't quite shoot as well as a Colt. But the Smiths that were built (accidentally) to better tolerances were every bit as good as the Colts.
As much as I love Ruger, the one drawback to Ruger's double action has been its action. It just could not ever get quite as crisp as the crispest Smith. Thus, even good shooters had to learn to overcome the overtravel after they squeezed the trigger. If you don't have as much overtravel, you don't have that extra element to master. As actions go, however, I didn't like Colt's actions as much as I did Smith's.