What are we really talking about here, and how much can we really know? Formal education? A nice uni is no guarantee of smarts, and let's face it, being a European royal means you're going to get in wherever you want.
Plus, some royals like Haakon and Fred went to nice but public secondary schools. Felipe spent a year at boarding school in Canada.
Eton may have prestige, but I've heard that the students have an abysmal understanding of life outside of their particular socio-economic class. Hard to instill empathy & compassion in a Hooray Henry.