Auger style muffler vs Ultraflow/Magnaflow etc..

[whytry]

I have been trying to find out the main benefits of switching from a Flowmaster 40 series to either something like a Lobak (auger style) or just replacing my existing with either a Magnaflow or Ultraflow muffler. Is there a reason the Auger style are not used more? There are several mufflers out there now that are pretty much a straight through design so I don't see the how loud the muffler is being the main reason to choose one over the other, and from what I can tell from internet searching the Lobak's seem to have, in general, have done well with increasing HP.... Is there something I am missing?

My buddy has Lobak's on his 65 Mustang, and it is pretty mild of a motor, but his Lobak's give it a nice deep low rumble at idle and cruise, but WOT it sounds nasty, and by his own admission there is nothing wild about his motor...