Since migrating into the Second Life wiki, the Second Life viewer directory has been resorted rather interestingly. By crash rate.
Second Life viewers (both first party and third-party) send crash statistics to the Lab (along with other statistics). This most recent incarnation of the viewer directory lists viewers from the least-crash-prone to the most.
Interestingly, Linden Lab places all of the official viewers above all of the third-party viewers, with the assertion that they crash less, which doesn’t really match up with my experience, but does list the first-party 1.23 viewer right at the top (which very nearly does).
I don’t know how often the ordering of this list might be updated.