It's obviously anecdotical but I know both many smart persons without higher level education and many 'not-so-bright' persons with university degrees. However, all those with degrees have parents with degrees and those without come from lower class, for the lack of better term, families. If your parents have never set foot in an university and worked manual labor all their live, you are less likely to even consider h…
Those with degrees tend to be great with theory, but lacking in practice or application. Mind you, they are otherwise pretty bright people, so I don't fault them. They simply didn't get the corrective feedback needed along every step that tends to come with putting an idea into practice. I think of the engineers I work with daily as I write this. They can design new product in CAD all day, but have never built one, which hampers the implementation of their design in the real world and frustrates them.
Those who learned by doing, as opposed to 'studying to the test' such as myself will have a much stronger grasp on the ways things might go wrong (or in some cases, not actually be possible even though it works on paper or in simulation) and be better prepared for it. However, we also tend to have considerable gaps in our theoretical knowledge, and tend to try to make up for it by our ability to quickly adapt or problem solve.
Combined, I'd say the two types of people do make a good team, so long as each is compensating for the others deficiencies in a mutually beneficial way. I rather like the engineers I work with, and they seem to like me, so together, we are pretty valuable to each other and our employers. With other teams, I see this relationship break down when one side starts with the "they don't know anything" attitude.