Not necessarily.
All unions I have been associated with, have their hand out wanting money, normally a percentage of one's salary. As a group, a union normally has more power, as there is usually an affiliation with some other union but of course is much more long winded, when decisions have to be made.
As a group of employees (non union) getting together and taking direct action ie stop work, on some issue is slightly different but just as effective, if they are prepared to hold out.
That's the way I see it.