Adderall is what's called a mix of amphetamine salts, containing both dextroamphetamine and levoamphetamine in a ratio of 3:1.

Vyvanse is Lisdexamfetamine which is converted in your body to dextroamphetamine and lysine.

The main difference between the two is that vyvanse has to be converted to be used, and that conversion produces lysine which slows down the action of the amphetamine.

This results in softer slopes of onset and can feel less intense than adderall.

Keep in mine though that both adderall and vyvanse have about the same abuse potential once you reach about 100% over a given prescribed amount. It might be that adderall is more likely to be over prescribed or given to stimulant naive people, whereas vyvanse is more likely to be given as an alternate medication and where the slowing of its action makes higher doses feel like less.