why are getting multiple opinions better than just one?

If your in need of an advice you would most likely like to hear one from a couple people. Why? because you would like to be able to get as much help possible. You could lean more to one opinion or the other or maybe even all of them.

If you ask a friend to revise a project you have worked on you would like to get an opinion on how to fix many things, you wouldnt just like one and have the rest incorrect or leaving it unrevised. You have more to rely on when you have more than one opinion.

Why are multiple opinions better than one? because you have more to rely on with more than one opinion

So if your ever in doubt ask more than one person for an opinion, its extra help and you get to choose what opinion you want to help you or use all of them.