All annual sweet peas are scented but some are more fragrant than others.  Your sense of smell, the time of day you pick a bloom and a whole load of other factors will affect the fragrance from a sweet pea flower (or your perception of it) - you can read more about that in my blog post 'The Most Fragrant Sweet Peas'.  Over time, the consensus has been that these sweet pea varieties have are the most heavily scented sweet peas.  Their names really give away that every single stem will fill the air with a deliciously sweet, fresh fragrance.