I had computers as a hobby for many years, starting out with FreeBSD 2.2.8 when I was in 8th grade and teaching myself C and dabbling in a few other things as well. I'm 25 and have a legitimate 5-digit ID, not that it means much other than I got started with being a nerd at an early age for some reason signed up for Slashdot. I thought I was going to be a Comp Sci major, but then I quit and studied English and Classical History instead.
I still kept up with Unix-y things, and futzing around with Perl and stuff like that, and after an endless string of half-ass pseudo-success after college while trying to do the "english major" thing, I bit the bullet and got back into computers. I've been employed for the last year and change as a Linux admin at a web hosting company, and just got a new job that I start next month where I'll probably have to write the occasional C code again, too.
Now, I think I'm a reasonably competent programmer -- definitely more so than one would expect from a liberal arts major, but I'm definitely not a computer scientists. I'll read algorthims books and study stuff on my own, but I think I lack the degree of comprehension that someone who had it drilled and tested in a formal environment would. I'm not a great programmer, but I can hold my own in the certain realms in which I need to write code, but computers are also not my entire life.
Most tech school people I have met are really only interested in computers and doing computer stuff. They're the ones that throw the memes around and use terms like "lulz," and as long as they do their job, I don't really care. But those I know who studied computer science are more likely to be able to talk with me about non-computer things, and I really appreciate that. I make my living in technology, but my hobbies and interests are wide-ranging, and I don't always just want to talk about computers. I also find that the university-trained computer scientists are more likely to be able to explain WHY they are doing what they're doing, why they made the design choices they did, and in general have a better understanding of the whole system rather than just doing things "they way they were taught" whether its the best or not.
Of course, I realize this is all just anecdote and not just data, and I'm probably going to piss some people off by saying, however I will stand behind the notion that university-trained computer scientists are going to be easier and more fun to deal with than someone with a more myopic view of their "trade."
Also, if you really want to get at why those with a 4-year degree from a "real" school get offered more and are picked first, its probably because those are the degrees that management understands, whether they understand the subject matter or not. Management typically has a 4-year degree from a real school, and so they'd rather hire people with a piece of paper they "get" the value of. Perhaps its an economic or educational prejudice, but such is life.