Depends do you want to spend extra to delete all the emissions crap or not. Personally I think the lbz looks better and I think the interior is better on the lbz, the lmm seems really cheap and is noisy.
As far as base mechanical goes they are pretty much the same
Is a down pipe louder then turbo back
With an exhaust only, it sounds like cats ****ing. With a full exhaust with the down pipe it is a lot deeper.