Id have to say, its all directional. If your behind the bike, the regular rearward exahust will be louder. if your standing at the right side, the exbox is louder. if your standing at any given location, its likely that regular rear facing pipes are louder.
I think that Termis are louder in comparison, but that might just because they carry more bass and actually direct it somewhere isntead of spitting the sound out into a box that directs it no where in particular.
My refrence point: is Chchader who i ride with all the time. From the rear, i cant hear his bike at all over my own exhuast (open udder) and my other friends termis on his 749s which i can hear all the time (cause its pointing at me).
if you WOT it, though, i doubt you can tell the difference cause youd be deaf already.
Interesting... I wonder if the exbox would be any better at keeping drivers from changing lanes onto you (from the right side).
I'd also think it would be louder from the rider's perspective when riding past walls and between cars.