I own a 686-6 and a 66-1 and find them both desirable. I can't favor one over the other. I'm sure whichever one you decide to keep, you'll be able to sell off the other quickly.

You did not mention exact barrel length, but I find the 686 to be perfect in 3 inch. I had looked at and tried a 2.5 inch but never warmed up to it, and the 6 inch always felt too barrel heavy. The L frame does have a higher bore axis than the K frame. When I first bought it I was so use to K frame's that it took me a little while to finally get it to shoot tight groups.

As for the model 66, it feels so well balanced and natural in your hand. Based on the near perfect model 19 it's hard to find anything to complain about. I guess my only gripe is I don't carry or shoot mine as much because being it's no longer in production, I'd like to keep it in as best shape for as long as I can.

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Ephesians 6 (Armor of God)