I've got a growing group of no-dash models but that's only because the first handgun I ever bought was a 6" 686 when they were first introduced. So I have a soft spot for the earlier ones. That first gun, after 25+ years of heavy use is still just fine so I wouldn't worry about buying an older one if you come across a good deal. I also have a 5" Stocking Dealer Special (no-lock so a dash 5, I think) that I seldom shoot but its a very nice gun with a great trigger.
You can't go wrong with any of them as a group, as long as the individual model you pick up came out of the factory alright and hasn't been messed with since. Good luck.
Wait a minute, I just picked up the 586 so let me please brag a little bit:
8"686, 6"686, 4"586, 4"581, 3"686 CS-1, 4"686 CS-1