Are girls better at gymnastics than boys?

Not always

Actually, girls are better in some ways than boys. First, girls are usually more coordinated, stronger and mature than boys of the same age. The good news. The bad news: girls reach their peak between 17 and 18 and many retire from the sport, while boys are just coming into their own in terms of strength and coordination. Also, because men are stronger physically women must be more technically proficient in order to perform some of the more difficult elements. For example, because women had to swing between two bars, they were forced to become more technically efficient. The same is mostly true on floor exercise/tumbling. Men generate much more power on this event, so again women must learn to be more technique-oriented. I guess the real answer is Yes and No.

My answer would be neither. Because you can't compare girls gymnastics to boys gymnastics because both perform on different apparatuses and do different skills. Boys strength excercises are hard than girls strength excercises because boys need to be stronger than girls because of the skills they perform, the strength excercises are also different and strengthen different muscles.