I don't think this kind of nitpicking between the different definitions of rational is very productive. Yes, rationality is the art of making the best decisions and yes that means rational people should be "winning".
Unfortunately, I don't get the impression people who identify with LessWrong or with Bayesian reasoning are all that successful in life. I don't get the impression that when people are exposed to LessWrong that their life improves significantly.
It takes at least a 1000 hours to learn the Art of Rationality (probably much more) and if after all that effort people are not noticeably more successful how can we possibly call rationality winning? The opportunity cost of studying rationality is immense so we should get a large return on that investment!
From my point of view it looks like the rational choice is not to study rationality. Instead learn to play the guitar, or take cooking classes, or do any other activity that makes you a more well rounded human being. People often attribute increases in happiness and life satisfaction to that sort of activities.
Alternatively, just look at the people who live the kind of life you want to live and see how they got there and follow their path. This isn't Bayesian reasoning with a prior based on aggregated life experience of your heroes (although technically it is), this is just common sense. This is the same conclusion you'd reach without studying rationality in depth.
It's fun to refer to rationality as the art of winning, but let's not forget that we say this with tongue firmly planted in cheek.
PS: if making a decision is difficult because you have trouble quantifying information then this is probably the solution.
Alternatively, just look at the people who live the kind of life you want to live and see how they got there and follow their path
When I was in high school, I wrote and ran a prisoner's dilemma simulation where strategies reproduced themselves via this mechanism. After every cell played several rounds against its neighbors, each examined itself and its neighbors to see how many points were accumulated, then either mutated randomly or copied its most successful neighbor.
I was trying to experiment in the fashion of vaguely described other simulations I'd...
Recently there has been a couple of articles in the discussion page asking whether rationalists should do action A. Now such questions are not uninteresting, but by saying "rationalist" they are poorly phrased.
The rational decision at any time is the decision, given a human with a specific utility function B, and information C, should make to maximise B, given their knowledge (and knowledge about their knowledge) of C. It's not a decision a rationalist should make, it's a decision any human should make. If Omega popped into existence and carefully explained why action A is the best thing for this human to do given their function B, and their information C, then said human should agree.
The important question is not what a rationalist should do, but what your utility function and current information is. This is a more difficult question. Humans are often wrong about what they want in the long term, and it's questionable how much we should value happiness now over happiness in the future (in particular, I suspect current and future me might disagree on this point). Quantifying our current information is also rather hard- we are going to make bad probability estimates, if we can make them at all, which lead us into incorrect decisions just because we haven't considered the evidence carefully enough.
Why is this an important semantic difference? Well it's important for the cause of refining rationality that we don't get caught with associating the notion of rationality with certain goals. Some rationalists believe that they want to save the world, and the best way to do it is by creating friendly AI. This is because they have certain utility functions, and certain beliefs about the probabilities of the singularity. Not all rationalists have these utility functions. Some just want to have a happy home life, meet someone nice, and raise a family. These are different goals, and they can be helped by rationality, because rationality IS the art of winning. Being able to clearly state ones goals and work out the best way to acheieve them is useful pretty much no matter what those goals are. (pretty much to prevent silly examples here!)