Yes, undoubtedly top schools give a better education. In part it is due to a more rigorous curriculum in fundamentals and less vocational as lower-end schools tend to be. It's also because of distinctly intellectual atmosphere and the fact that almost every student is very smart.Is there difference in actual education?
The network is a side effect, though a very useful one. Of course, the prior alumni that form the backbone and that helps a lot. But also whenever you get so many smart, driven people graduating there will be enough success stories among them to create a network in itself. I am talking about the current state of ultra-competitive admissions, of course, not 40-50 years ago when it was mostly a good old boys club.