Well I have been prescribed both and I am not a doctor, scientists or an expert, I just read a lot.
Ritalin is comparable to cocaine in effects and duration.
Adderall is simply amphetamine (oh I do love amphetamine) so in comparison is more energetic and last more that ritalin.
For ADD both works, it depends on the people taking it. Some responded better to adderall or ritalin. Both are great to treat ADD.
I prefer Amphetamines over Ritalin just because amphetamine give me the energy I need and ritalin don't, it even get me sleepy.
That is that. If you have a question of my post I will gladly answer, my English is not the best.