I'm with PurfectlyInsane on this one.
The only true way to test the theory that regular is louder than inverted is to build two boxes with the same net volume, with one inverted and one mounted normal. Plus, it has to be tested with multiple subs. The subs also have to be broken in so the T/S parameters are close to the same. They have to be powered the same, aligned the same, EVERY variable besides the driver mounting has to be held constant for this to be a valid test.
Not gonna lie, i do see ignorance on this site from time to time. Just saying...