What I do in determining what to do is work backwards from:

a) what I want out of the frequent flyer program: awards for which class/routes; upgrades for which classes/routes; lounge benefit possibilities; etc.

AND

b) what can I achieve given my work/leisure travel needs, ticket fare/class mix, etc.

Then after answering those questions and a few more, I decide which programs make the most sense given my answers to those questions.