Both the GP100 and 686 are quality revolvers, each with their strengths and weaknesses.

The lockup on Ruger is a great design.
The cylinder release on Ruger is a great design.

The drawback to Ruger, IMO, is the "tang" grip frame. The aftermarket options for grips is rather limited for the GP100, due to this awkward grip frame design.

The 686 is much more refined, in finish and overall QC (in my experience) and everybody and their cousin from Taiwan makes grips for the 686.

Can't go wrong with either, unless you get one built on a Friday afternoon, in which case......both companies will square you away with call tags and good service.