A BIG consideration is how much, and what are you planning to shoot in them.
If you are going to shoot 38 Special ammunition 99% of the time the 66 will last forever. On the other hand if you are planning on a steady diet of HOT 357 Magnum ammo, and lots of it. The 686 is the easy choice.

I had a 2-1/2" 66 and I did not warm up to it for some reason. I ended up trading it for my Barbecue Revolver an as new 2 Inch 15-5.

My most carried revolver would be my 66-2 with 3" barrel.

I conceal carry my: 2" 15-5, 3" 66-2, 2-3/4" 315NG, 2-3/4" 310NG, and 3" 625.
I can tell the difference in weight between my 66, and the 625. I suspect the 686 snub is enough heavier that you will notice the extra few ounces. The big consideration is Tollerance. I carry all the above revolvers excluding the 625 and never notice I am wearing them. I do notice the extra weight of the N Frame. The 686 may be within your tollerance level, and carry fine.
The holster is another BIG consideration. I carry all my revolvers in Pancake holsters.

Tough decision.

If I managed to come up with a 686-4 SIX Shooter, with a 3" Barrel, I would be carrying it daily. That is at the top of my Christmas List.

Bob

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