My 1961 6" Royal Blue Python would be my favorite, with the absolute best finish. I've never shot this one, I'm the third owner, and other than Colt, I don't think it's ever been fired. I know the second owner stated he didn't fire it, and he had it 25 years.
The 1974 4" RB Python would be #2, and it shoots like a dream. Compared to the same vintage 27-2 that I bought for my son, the Colt trigger is just soooooo much smoother, and while the 27 is a fine, fine firearm, I just don't think it compares to either Python in fit, finish or refinement.
My current dash 642 is the most used, my 17-4 is a tack driver, and the bird's head HRR and 6" Anaconda are the most fun.
I liked my first release 3" .327 sp101, about the perfect size, but heavy, carry piece when the factory grips were tossed. Should've kept it. Also miss my 4" 1985ish 686 and 629 Classic DX. But was young and dumb.
As it is, I need more revolvers. 6 just isn't enough.