The Third Party Viewer Directory is updated from time to time. Oz Linden changed the TPV List 4/16.
The viewers with enough users to generate reliable stats and that participate in crash reporting are listed in the first section of the list in the order of stability, least crashes. In this update Catznip is in the first position as the most stable.
The Imprudence Viewer is second, Singularity, Phoenix, Firestorm, and RLV follow.