Here's the deal, OP.
With most used guns that are still in current production, value is a function of depreciation. The value drops a bit when you carry it out the door, it drops with wear, and it drops when improved versions of the product hit the market.
Classic S&W revolvers are not exactly subject to these rules. Anything new enough to have a Hillary hole is, but pre-lock S&Ws might as well be completely different models as far as the average revolver enthusiast is concerned. The difference between older S&Ws and new production guns is almost startling. I have a 625-8 Performance Center gun and an old 17-2 .22lr. The old .22 is a much nicer gun than the 625.
So, how about that pricing? S&W seems to build revolvers (excluding J-frames) in small volumes, so they can be tough to find. If you can find a brand new 586, you're probably looking at $700+, anyways. But, for the sake of this discussion, let's say that you find a brand new 586 and a near mint 586 no-dash in the same store and at the same price. Most of us would take the old one, hands down, no dice.
But, if you're worried about hurting the value and ending up upside down in the gun, you can wait until you find one with some wear, and buy that one for a bit less.