"What are the differences among various brands and forms of stimulant medications?"
Clinically, there are few differences between methylphenidate (brand names Ritalin, Daytrana), dextro-amphetamine (brand name Dexedrine), and the mixture of the salts of dextro- and levo- amphetamine (brand names Adderall, Vyvanse).
Some individuals respond better, or have fewer side effects, with one than another, and people often try several before finding the right medication for them.