Whats the meaning behind nothin on you by B o B and Bruno Mars?

in nothin on you he's sayin that there is no girl better than her. that he's been all over and she's the best.he's sayin that they don't got nothin on her=)need you now is about a breakup that shouldn't have happened=) that's wierd!!!!! omg!!!! i was listening to nothin on you when i was answering that question and as soon as i finished typing about nothin on you and started typing up need you now, need you now came on the radio!!! sooooo wierd!! =P