Yeah, I too think the MBRP sounds the deepest, but they don't seem to be much louder than stock. It's hard to tell volume levels through video though.
Here's another good video I found of the MBRP's, and the car is actually a manual. There's too many auto trans exhaust videos and not enough manual IMO.
MBRP Exhaust Mustang V6 2012 - YouTube
I really like the sound of these, but I also like the Magnaflow streets, and Borla Touring. It'll be hard to decide without hearing them in person, but I guess I need to get the car first and then worry about exhausts later after my bank account recovers a bit.