To make a direct link of the "holy grail" .357 of each manufacturer, and focusing on .357, the Python Equivalent of the S&W line is the 27. High finish, no-holds barred flagship gun until discontinued in - uh, '94 I think.
The "Registered Magnum" is just the pre-war limited edition model. Uber-collectible. The more pedestrian but functionally equivalent model is the 28, the less-highly finished but mechanically and dimensionally identical .357.
But a direct, head-to-head gun is the 586/686 - dimensionally very similar to the Python, same weight, frame size, etc. It would take an action job to make it quite as smooth as the Python, but after that it is more robust. Generally not as highly finished as the Python, but with the extra $500 in your pocket after the purchase and action job, you can get that fixed.
So, that aside, to address your question in parts:
1) a Revolver you don't mind putting a little money in? A 27. $800 to $1100, but they ain't going to loose that value. Want to make money? A 28 or early 686 - not making them like that any more, either. I can't do a thousand for a 27 right now, but I have one each of a pretty 28 and 686.
2) Not a bad word to say about? All of the above. There are no weak points to the 27/28, or 586/686. There are to the 19 and 66.
Now, you want to go REALLY holy grail, we talk about the .44 special Triple Lock like like earplug mentioned. Now that's a "Holy Grail" gun. I have a 1916 variant in .45LC, w/o the yoke latch. Otherwise identical, but not the "Holy Grail," alas.