As to the "Holy Grail" of 357s, the Python is up there, but too common. The "Holy Grail" would have to be an original S&W Registered Magnum, with box and registration papers of course. But then I wouldn't take that to the range, much.
Anyways, between the S&W 66 and the King Cobra, get the snake. Unless you plan to shoot the daylights out of it. I have fired only one King Cobra, years ago, but when the Pythons are all in museums the KCs will be their successors. I believe the actions are almost as smooth, but not quite as delicate as a Python. The Dan Wesson is a good suggestion also, especially in a complete pistol pac. It all depends on which flavor you like best, I usually prefer something just to be a little different.