The problem with caffeine is that it tolerates so fast, and is so addictive, that it’s still unclear if you gain any benefits at all after a week or so. The first buzz may be useful, but after that…? Some smart drug.

Modafinil, on the other hand, is stronger and takes a lot longer to lose effectiveness (if it does, which is a longstanding difference between the academic community and the nootropics community).

I’m pretty sure caffeine has it beat by a few centuries.

I’m pretty sure you have not tried provigil.

Caffeine merely keeps people awake, even when they should not be. Perhaps good for manual or routine labor. Not as good as tDCS, according to tests.

Provigil has been described as allowing one to concentrate much better.

Big difference, unless you are some sort of sperglord whose attention and focus cannot be improved short of divine blessing.