Slate star codex 2016 nootropic survey results
slatestarcodex.com
slatestarcodex.com
Sure, it is possible that personal responses vary. But unless people do some blind trails, I am very skeptical of the claims (various placebo effects when acting _and_ grading).
If one makes you giddy and bursting with creative ideas and another gives you drone-like immunity to distractions, they can't be linearly converted to equivalent doses of caffeine.
I think the survey's score chart is best understood as a "how much do you like it" ranking instead of a conversion chart.