I don't have ADHD but I've used both drugs for work, and Adderall works better, but Modafanil is not addictive. Modafanil gives you a similar hyperfocus without the euphoria of amphetamine. It has a high tolerance curve. It also has a flatter dose response curve (i.e. taking two modafanils won't give you twice the effect).

When my health insurance lapsed I was put on Adderall because despite modafinil being a generic, it was still too outrageously expensive to pay for out of pocket. I got no euphoria from Adderall. I was able to stay alert but I was jittery and wildly irritable. As soon as I was able to get good insurance again I dropped it for modafinil. I guess I should be thankful that Adderall didn't appeal to me due to its addictive potential.