Nation wide, boys have better SAT and girls have better high school GPA. Boys are uaually better at comprehensive tests and girls for knowledge closely related to courses. Boys' capability distribution are more skewed and girls are more close to the means. This means boys have more top talents and also more bad performers. This is why boys have better top performers at highly competetive competitions and girls are better at usual course studies. If the above distributions are true and MIT has about 50:50 gender ratior then definitely it's easier for girls to be admitted to MIT.