If you want to do some serious shooting with the gun that involves magnum ammo, I would choose the 586, an older one from the '80s though. That gun will hold up much better to extensive shooting, especially if you get a Python with cylinder collar design. From my observations of S&W and Colt revolvers, Colt V springs start wearing out quicker and easier. I rarely see any of the mechanical integrity signs on a S&W that I see on Pythons.
Accuracy won't be much of a factor for most people, as both guns can probably shoot better than most. Ruggedness has already been discussed. So it comes down to how much do you want to pay. A nice 586 probably under $1K, a nice Python probably about $2K-$2500 unless you really know what you're doing.
Comes down to personal choice. I had this same dilemma when it came to my magnum carry gun. Could have had a like new 686 2.5" for $800, but ended up going with the LNIB 2.5" Python for multiple times more because I simply prefer the action design and can tune it better. Ended up getting a gun that had schmucks working on it and they fudged a bunch of stuff up. Good thing I can repair myself, so you have that to worry about with Pythons too, paying large money for a gun that needs repairs if you want it to really run.
My thoughts. (if you asked this on the S&W forum, it would have been an overwhelming 586 choice, so it sounds like you want a Python because you came here.)