Can someone rank the unions on effectiveness and explain why?

I've been seeing a lot of posts on unions lately and I am curious on the following:

1. Which unions are the best? (maybe rank them if possible?)

2. What makes those unions better or worst than others? (e.g. is it as simple as membership rates? Like 95% vs 85%?)

3. What can I do to help increase union effectiveness other than just paying my dues?