Rodolphe is the seducer who calculates: experienced, a landowner, he plans to win Emma soon after meeting her and abandons her when love becomes a commitment. Léon is the shy young man who loves her without declaring himself and only becomes her lover later, when he comes back from Paris no longer as shy as before.
Both speak to Emma in the language of her novels. Léon returns the formulas she gives him at the welcome dinner; Rodolphe uses them at the agricultural show, already knowing the effect of each sentence. Rodolphe plans the seduction on the way home, after their first meeting; Léon writes letters that he tears up and leaves for Paris without saying a word. With Rodolphe, Emma is the dependent one; with Léon, in Rouen, the relationship is reversed, and it is he who "behaved as though he were the mistress."
The end of each affair also separates them. Rodolphe breaks it off with a letter composed for effect, a drop of water standing in for the tear. Léon drifts away little by little, pressed by his mother and his employer, until he sees in Emma a danger to his career. At the decisive moment, however, both fail in the same way: Léon comes back empty-handed and escapes with the false promise of a wealthy friend, and Rodolphe answers "I haven't got them!"
For Emma, the difference between sincerity and calculation is invisible, because both languages come from the same novels she has read. That is why the second affair repeats the cycle of the first, and with Léon she ends up finding the boredom of marriage. Both possessed her without risking anything for her, and both draw back when she asks for something concrete.