The BL nobody has actually heard yet, but it is supposed to be more SPL and the Q is SQ. With the BL, it can get more expensive because you can add cooling and stuff to it to make it handle more power...
dont get me wrong, it will still wang like a champ, just IMO i would load it for the extra what like 50 bucks or something, how much power you goiung to be using M. Mann?
I know I would usually get the fully powered but I've been wanting an Fi for a while and when the BL came out I said I gotta get it, and I really only had enough $$ for non-loaded
bl and the Q are totally different drivers. Q is more sq oriented with good output. the bl is a straight out spl driver with some nice sq.
if you want to compete and want to push a sub beyond its limits, i'd say go with the bl but if you want that smooth sounding and good blending sub, go with the Q.
i say again the 2 subs are for tatally different applications.
"The BL doesnt have the same amount of Xmax as the Q, and doesnt have the same bottom end output in some cases. But it does work better in SPL applications"
, but it will still be sick. I'll let you know how it is 
I'm so excited