The XXX and the MT are very different drivers for very different applications. Comparing them basically means you dont understand the role each one is meant to accomplish.
If you want to compete in SPL and (most likely) own the locals, the MT would be the obvious choice of the two. If you want a loud daily driver that sounds very good while beating the snot of out you, chose the XXX. if you mean the 06 or newer XXX, skip it altogether.
XXX is nobody's "cute little sister". XXX makes its own name in many ways.
Speakers do not create energy, they transduce it. Therefore RE does not have a 'most powerful' sub. Again, different drivers meant for different applications. Your generalizations dont help much.
No offense, but do you have any idea what you are talking about? More watts doesnt automatically equal higher output. Aparently speaker/system efficiency means nothing?