You still havent mentioned whether you have room treatment or if you are using any room correction software for the 2 subs. If a sub is only playing some 30Hz and above and if there are no offensive room modes in that range, of course it will sound tight. Where as, if a sub can go down to 20hz and if there are room modes in that range, it will sound boomy. It is not the fault of the subwoofer. It is the fault of the room. I mentioned so many times that subwoofer measurements are done outside in order to avoid room effect.
You need to use Audyssey or Antimode or any other room correction to correct/calibrate the subs and then compare. You are comparing one sub that cant do below 30Hz LOL! with a sub that can go down to 20hz and may be affected by room modes. You claim to be the "science" guy. But what you are doing is so unscientific LOL and say that scientific facts to prove your arguments are not necessary? I guess the more you argue on these lines, the more credibility you lose in this forum. Go home :-)