I am biased as a 686-3 owner who displays the box proudly. I think they are both great, I am just surprised at the price of the 686. I prefer stainless over blued due to the lower maintenance requirement, but there is no doubt blued guns are prettier.
Seeing as the 586 has uglier grips, no box, and is more expensive, it would be hard for me to argue in favor of it. Ultimately choose what you fancy most, but to me this is an easy decision, the 686 hands down.