Colt = Python
Ruger = GP100
S&W = Registered Magnum / The 357 Magnum / Model 27
Whoooaa...with add due respect sir, the Security-Six has to be Ruger's .357 flagship.
Why?
At the time it was produced, it was many times stronger than its competition. While the S&W K-frames would fire about 2,000 hot magnum rounds without parts replacement, Skeeter Skelton said he knew of three Security-Sixes that had 30,000 magnum rounds each. One was spitting a little, he said, but it was still serviceable. Colt's Python was hard to beat from an accuracy standpoint, but it still has a tiny pawl/hand that wears quickly. Some shooters have hard chromed their pawls to stop the wear, but the Security-Six still beat it strengthwise.
The 686 has to be the flagship of S&W, but the Ruger GP-100 can't match the accuracy and it's a toss-up in strength. And while it may be a tad stronger than the 686, it doesn't add any real advantages over the S&W.
Bill Ruger said he never made a dime off the Security-Six revolvers, but it was a powerhouse medium-frame gun, and the 6-incher was a fantastic hunting pistol! The GP-100 is a bit chunky and picking up a moving target with full underlug barrels is a real challenge. Carrying the 6-inch hunting or camping is just not something I'd enjoy. But I did think the S&W 66 and Ruger Security-Six were astounding.
Just my view. Other opinions may vary.