1. While CS students have a broader array of programming knowledge, they have narrower perspective about it. By this I mean they have difficulty distinguishing their own programming experience and knowledge from that of the world as a whole. They assume everyone learned Java in CSE101 so they can't fathom how some one could program Ruby without being able to explain it using Java-esque CSE101 terminology.
2. CS students participate in open source more. Self-taughters usually do so in order to complete a direct objective (i.e. make a site, sell some widgets), they weren't exposed to the culture or peer recognition around programming that comes from years of academia. CS students are often encouraged or required to participate in open source projects. This sometimes leads to the false insular belief among the educated that all "good" programs work on open source projects. This pops up on HN every now and then.
3. CS students like libraries more. My guesses for why this is might be: (1) the academic exercise of writing your own libraries; (2) libraries are a generally more academic approach to programming where you write code "by the book" and work on many what-if possibilities; (3) it's 11:00pm and you need to submit your code in an hour - you don't care about maintainability - so shove a library in there to eek it out as fast as you can. Self-taughters don't have such academic exercises or deadlines in their learning; and they'll usually be maintaining their code for a long time, which discourages libraries in my experience.
These are my observations from the coders I've worked with. Of course, there are exceptions, I know there are many self-taughters who use libraries and work on open source, but just not as many CS students.