Conversation so far:
What was it like in the early days?
In 1925, the Masquers Club was formed by actors discontent with the grueling work hours at the Hollywood.
Were the actors in favor of this?
This was one of the major concerns which led to the creation of the Screen Actors Guild in 1933.
When was the union started?
Academy of Motion Picture Arts and Sciences, which at that time arbitrated between the producers and actors on contract disputes, had a membership policy which was by invitation only.
What were the advantages for the actors?
CANNOTANSWER.

Question: Who received the most benefit from this union?
Self-contained rewrite: Who received the most benefit from the Screen Actors Guild?