There are very good reasons for not getting a no-dash 686.

1. If you, understandably, do not care about the dash changes you can possibly save yourself some money and buy a cheaper one. You could also possibly save some time, too, by not being picky.

2. If you want to replace the front sight it's integral to the frame and will be costly to replace, and far fewer are capable of doing this themselves.

3. If you want a round butt grip you're out of luck. If you all ready have conversion grips you want use you're out of luck.

4. Mounting optics will be more costly and more time consuming. It may also lower the value of your gun.

5. It may be unsafe without the "M".

6. If you want a Plus model you can't have a no-dash or a few others.

7. No lifetime warranty. Buying used you're technically not covered by any warranty. However, anecdotally, S&W appears to apply warranty coverage - to those guns that had the lifetime warranty - regardless of first owner or not. Which can provide value.

#2 is a deal breaker for me, although I'd likely be able to make a trade for one with a pinned sight.
#1 isn't necessarily a deal breaker, but for me and my usage I have no reasons to pay more for something that doesn't provide more value to me.

Contrary to the every-older-Smith-&-Wesson-is-a-better-Smith-&-Wesson rote opinion this absolutely is not true. Like so many things involving gun purchases *your intended use* is the biggest factor.