Rationalists are the ones who win when things are fair, or when things are unfair randomly over an extended period. Rationality is an advantage, but it is not the only advantage, not the supreme advantage, not an advantage at all in some conceivable situations, and cannot reasonably be expected to produce consistent winning when things are unfair non-randomly. However, it is a cultivable advantage, which is among the things that makes it interesting to talk about.

A rationalist might be unfortunate enough that (s)he does not do well, but ceteris paribus, (s)he will do better. 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")".