I can compare the Outlaw subs to my Hsu ULS-15s, which use Adire's XBL^2 technology, and of course the ULS subs sound cleaner, but these are much more expensive, powerful, sealed subs vs large ported subs, so its not a very useful comparison. I have no doubt that a sealed 15" using TC Sounds, Rythmik, XXX, or JL Audio is going to sound better.
But for a ported 12" with a medium powered amp, the Outlaw sounds terrific, and has a ton of output, it will be hard to top, and I would guess the FV12 wouldn't have any perceivable advantage and in the deep bass would be at a disadvantage. That's just a guess though, and I would like to hear it for myself. As for the down-firing ports, I can tell you they have enough clearance from the ground to sound good. I have compared them to my Hsu VTF3's, which is very much alike albeit the ports are in the rear on the VTF3s, and I can't really tell the difference. Maybe I should do a closer listen however, as I didn't really do a very thorough comparison. But again, I have the Outlaws raised about an inch higher than the stock feet allow. The Outlaw subs can also be placed on their side to be front firing if there was ever a port clearance issue. But certainly one reason the ports are on the bottom is to lessen any audible port noise, as well as for aesthetic reasons. Anyway which sounds sharper is all guessing until a blind comparison can be done, and even then what sounds better is a matter of opinion.