there's a nerve within a woman's body that causes orgasms to be so strong, and if a man/woman hits that nerve with certain force, it can make it longer and stronger. And a possible reason it's harder for women to become aroused is the fact we lack the endorphin testosterone, which strengthens libido and drive within a man. Us girls have estrogen, which moreover deals with emotions and our drive. Testosterone acts fast within guys, but within girls, estrogen takes a little longer to take effect
(I know all this stuff from one episode of Grey's Anatomy, you learn some stuff)