Re-reading the text, I'm not actually sure where I got this, but last time I read this I parsed that bit as referring to how intelligence and rationality affect so many different aspects of life, and often in a multiplicative or exponential rather than additive way - if person A is 10 IQ points smarter than person B, person A might be able to learn twice as many useful, relevant concepts, and gain 10 or 100 times as much utility from the same situation by applying those concepts. It doesn't imply that A is a better person than B by any other metric, but intelligence has that potential in a way that health or home country or happiness set point mostly don't.