I remember about 6 years ago sitting in the staging lanes on a 90 degree day with the car next to me just shooting alcohol fumes in my face with his fender exit headers lol, I thought I was gonna die and I really hoped it was just a fad that would pass soon but it has definitely gotten pretty popular.
I'm sure it makes pretty much everything about a race car easier and it certainly would have eliminated my exhaust system nightmares getting up on my trailer.
I doubt a 9" bullet muffler will be any different than open headers. Now if you can fit a decent muffler in there with some stainless packing it could knock alot of sound down and still have the benefits of fender exit.