I was recently asked about how being self-educated affected my programming abilities in any way. I hadn't thought the question through prior to this, so I gave some less than satisfactory answer, meandering on about how it was a mixed blessing, or something to that effect. This isn't really a very good answer...
I'm an autodidact computer programmer, and formally educated physicist, so I'd like to think I have seen a decent cross-section of both informal and formal education.
Having given the question some thought, I would like to posit that autodidacts will ultimately prove to be superior at their craft. I'd like to emphasize that this is a pretty weak causal relationship. Suvivorship bias is arguably a strong effect at work here. Successful autodidacts would likely also be successful in formal education, whereas those who struggle with formal education will surely not make the cut in autodidacticism. Hence, most mediocre programmers can be assumed to be formally educated.
That being said, the successfully self-educated do possess a number of advantages. Learning has always been the autodidact's lifelong personal responsibility, and usually when you learn of your own volition, what you learn tends to ingrain itself fairly firmly in your mind. The act of furthering their learning is also something the autodidact performs habitually. Furthermore, in order to make it very far, the autodidact will need to develop some fundamentally useful skills in problem-solving and lateral thinking.
The formally educated are subject to entirely different dynamics. While they're probably going to be exposed to a broader spectrum of knowledge, following a fixed curriculum that makes few concessions to whether the student is susceptible means that central knowledge will be lost. Emphasis is on passing exams, not on deeper understanding of the subject matter, and passing exams has never been easier. I have also seen more than a hint of CS graduates ceasing their learning process the day they graduate. It's sadly fairly common that people with five year working experience have merely accumulated five years of one year working experience.
The singular drawback of self-education is that it is a lonesome road. It can be very difficult to find peers to bounce ideas off.
Although to repeat my reservation, it's of course always going to be hard to separate the selection bias from the effects imposed by the different means of education.