Can't decide: Both guns are 7 shot, medium frame, 4" barrel. Both have essentially the same overall length. The only differences I can see are that the 686 has a full length barrel shroud, and so is a couple of ounces heavier(not a concern) Other than that, the 620 is about $40 cheaper. Is there something I'm missing? Obviously the less expensive gun would be my first choice, but then I got to thinking: having the full length shroud would (theoretically) give the barrel more stability, therefore better accuracy, but with a 4" barrel, does that really matter?