2 Rockford Fosgate P3 15" 1000Wrms (for the pair) or 1 Kicker 08L7 15" 1000Wrms?

I want to know which option will be better for SPL. I can't imagine one 15 being much louder than two 15s at the same amount of continuous power but I don't really know much about how loud the RF's get I just know that they are good for SQ and I do know that the L7 is all SPL. Disregard amp & price and both will be in a vented box.