Balpa
I have not been long enough in Balpa to commen their performance. So far they have done a good job. Not excellent but ok. I've been in unions which were not as effective as Balpa. But its mainly the size and lobby which makes them rather effective. But when it comes to a certain issue in a company, the Crew Council has to do the job. So it depends on their performance. I think in nowadays aviation business you do not necessarily need to be in a union unless you work for the bigger airlines such as BA.