It's time for the ultimate fashion showdown! We're putting Jennifer Aniston head-to-head with Mariah Carey on this one! Both ladies rocked a gorgeous black and white Valentino gown, but we want to know who you think wore it best? Jennifer rocked the gown back in November to attend a gala. But leave it to Mimi to put the glam effect on the gown months later at an event for American Idol! Are you a fan of how Mariah styled the dress, or do you prefer Jennifer's more simple twist? Weigh in below with your comments!