Kicker L7’s or Comp VR’s?

Me and my bro were sittin here trying to do some figuring on our systems,and we asked ourselves these questions. Which would be louder, 3 l7 12's with about 800 watts to each one, in a ported enclosure, or 3 Comp VR 15's with 650 to each, in a ported enclosure. We know that the Comp VR system would most likely be cheaper,and it might hit harder. He has a S-10 x-cab,he is going to put his system behind his seats. Now for my truck, I was wanting to know which would hit harder, 2 L7 15's with a kx1200.1 to each, in a ported enclosure, or 4 Comp VR 15's with the same amps, in a ported enclosure?? I have a '97 Silverado x-cab. Also, is it true that polyfil lets you reduce your box size by 20%, and fools the subs into thinkin their subs are in a bigger enclosure?

                                        Thanx 4 the help- Trey & Wes