It's hard to compare plays with their movie counterparts especially if you haven't seen the plays acted out. But so far, it's working for me.
Golden Boy is one of Clifford Odets' most famous plays. It has dialogue with bite, characters that are real and a really excellent story. I like how even though the main character Joe Bonaparte is a boxer, the story doesn't entirely revolves around his fights.
The film stars Barbara Stanwyck, William Holden and Lee J. Cobb. Stanwyck was right for the role of sassy agent moll Lorna Moon. Holden, then a newcomer, also fits for the role of boxing hopeful Joe. In short, they were right for their parts.
To get a little poetic, there's a good use of symbolism with one of the characters. The character is Mr. Bonaparte, Joe's father. He portrays Joe's conscience, which is actually pointed out within the text. He hopes that the boxing is only a temporary thing for Joe, each time it's brought up it pummels Joe harder than an opponent's punches. I love that symbolism.
Even though the ending was changed for the movie, the rest of it stays true to Odets' play. But personally, the movie lacks some of that bite from the play. The movie's good, but the play's better.
What's worth checking out?: I'd go with the book.