https://gwern.net/modafinil

On any specific aspect, there may be a stimulant superior to modafinil, but few stimulants come close to modafinil’s overall package of being a long-lasting, safe, effective, non-mood-altering, quasi-legal stimulant, and that is why it has become so popular.

It is overall a better stimulant than caffeine or the amphetamines[11], and targets different receptors than the amphetamines[12]. The picture is good enough that some bioethicists are daring enough to go off their usual script (“the long-term effects are unclear; there may be unexpected side-effects or long-term consequences[13]—more study is required”) and abandon the Precautionary Principle and suggest that maybe healthy people using modafinil might be a good thing[14].