All depends.
Do you own other firearms chambered in .357?
How much .357 ammo do you currently own?
The 686 is a current production gun and is, frankly, a superior firearm compared to the 14, especially if the 686 has a 4 or 6 inch barrel. But, they don't make the 14-3 any longer and you can always buy a new 686 later on.
But if you don't own another .357 and you may have a lot of .357 ammo on hand, I'd be hard pressed to tell you to get rid of your only .357 in favor of a .38 special.
Good luck with your decision.