Looking at Julia's actions in the book, she seldom takes actions strictly to go against the Party's wishes. She does them simply because she wants to, as enote states: "Winston discovers that Julia is smart and funny and loves sex, and she doesn’t care at all about Big Brother. As for her membership in the Anti-Sex League, she is simply doing what is expected of her in society. A pretty woman with dark hair and freckles, she is basically a simple woman who doesn’t worry about the revolutionary implications of her actions; she does what she does because it feels good and right. She cares little about revolution and even falls asleep when Winston is reading from Emmanuel Goldstein’s revolutionary tract."
Winston, though, wants to actively rebel against the Party because he does not believe in the system and would like to bring it down (though he has a hard time coming to this realization because he can hardly think for himself). As enotes states, "A thirty-nine-year-old man who works in the Ministry of Truth, Winston Smith is fairly ordinary. His heroism is heartfelt, not out of false notions of rebellion for the sake of power and glory."