I think Surfin' USA's a tad bit funnier.
Iron Maiden definitely laid down the template for power metal. They put the vocals and guitarwork in place, and then Manowar and Helloween picked it up from there. Soon, Stratovarius and Blind Guardian would beef up the sound a bit, a lot in BG's case, but generally, Maiden hasn't had that double bass/keyboards feel. Their melodies are all on a different scale, too. I think power metal is played on E maj, while Maiden were always E min.