I think they're bad. beauty pageants only teach your children that only looks matters. There are many things you can do to help your children gain more confidence rather than putting them into a competition. When they lose, they will think that they're not pretty enough. Such things leads to depression, eating disorders etc.
I'm a makeup lover, but what's so cute about 9 year old with face full of makeup? Just let kids be kids, there's no need to rush them to grow up.