I will posit this as my opinion - it is easier to change opinions than it is to change beliefs. The line drawing between opinions and beliefs is probably fuzzy, however. I would also suggest that your own personality will affect whether seeing facts contrary to your own opinion will cause you to change that opinion. I think this opinion of mine gets some support in a recent paper (abstract published at Close Minded Cognition).

That paper determined that people scoring high in the desire for order, structure and preservation of social norms tend to be less successful at correcting erroneous beliefs when confronted by new information. For those people, a close-minded cognitive style negatively influences belief updating. (click on the title to see more)