The S&W 686 was specifically designed to go toe to toe with the Colt Python. The action of the 686 is superb and the gun shoots 125-grain and 148-158-grain ammunition equally as well, while Ruger's .357s tend to shoot 158-grain better. The 686 no-dash is about the best .357 I've ever seen roll off a production line. It's extraordinarily accurate. I assume that today's models are just as accurate. The Ruger GP-100 is a reliable gun, very sturdy and accurate, but it's just not in the same league. It's one reason I recommend people find a good Ruger Security-Six if they're looking for a decent .357 Magnum they can use for camping, hiking or fishing.
For competition or long-range use, the 686 is about the best .357 Magnum made today. And I'd say that even if the Colt Python were still being made. The Python was very, very good, but it wasn't better than the 686.
The no-dash is still my favorite, but the modern rendition of the gun is
most likely just as accurate and well made!