Maybe that could be the slogan—“rationalists do better”? With the implied parenthetical “(than they would do if they were not rationalists, with the caveat that you can concoct unlikely situations in which rationality is an impediment to some values of “doing well”)”.
By parallel construction with the epistemic rationality of the site’s name, perhaps “rationalists make fewer mistakes”?
By parallel construction with the epistemic rationality of the site’s name, perhaps “rationalists make fewer mistakes”?