What's the difference between adderall (dextroamphetamine and racemic amphetamine) and addrerall xr? when it comes to adults, for task focusing, which is better? please advise

Extended release: Adderall (dextroamphetamine and racemic amphetamine) xr is the extended release form of Adderall (dextroamphetamine and racemic amphetamine) (this means that the effects last longer than a faster release form). The longer acting form helps to prevent marked changes in levels of the medication. Some people like immediate release and some like extended release.