If you plan to some day compete with a revolver, I suggest moving up to the N-Frame 627, 8 shot, that uses moon clips. Reloads are fewer and quicker.
If you are set on the 686, then I doubt you will be disappointed with either the 6 shot, or the 7 shot. I bought a 4" 6 shot and never regretted not buying the 7 shot. It is a nice revolver and one I think everyone ought own at least one of. I sold it a few years after I bought the 627 and it was a hard thing to do even after I was totally sold on the 627.
When the number of people in institutions reaches 51%, we change sides.