Here's a breakdown:
Gaston has more screen time: He is the main antagonist and appears in many scenes, often driving the plot forward. He's a charismatic and larger-than-life character who is constantly on screen, making him seem like he has a big role.
The Beast has more emotional depth: He is the main protagonist and undergoes significant character development throughout the story. His journey from selfish and angry to loving and compassionate is the heart of the movie. He has more complex motivations and internal struggles than Gaston.
Ultimately, both characters are crucial to the story: Gaston's villainous actions create conflict and propel the narrative forward. The Beast's transformation and his relationship with Belle are the emotional core of the story.
So, who has the bigger role? It depends on what you prioritize. If you value screen time and plot influence, Gaston might seem to have a larger role. If you prioritize character development and emotional impact, The Beast might feel like the bigger player.