May 11, 2010 10:00 PM

Retna UK/Landov; Billy Farrell/

Just a week after Katy Perry (literally) lit up the Met Gala in her color-changing CuteCircuit LED gown, Rihanna proved she too could electrify a party, taking to the stage at London’s O2 Arena Monday night in a sweeping black drop-waist dress lined with what appears to be rows of tiny red lights. It’s no secret that Rihanna and Katy are close friends–having even taken tropical vacations together–so we can’t help but wonder if the two are also sharing style secrets. We’re not sure, but we love that the pop star pals are so sartorially simpatico. Tell us: Who wore her light-up gown better? –Marissa Patlingrao Cooley

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