thats what i thought u were referring to is the sound difference.. thats why i said i really couldnt help u is because ive only had a single outlet exhaust ive never put a duel on my avenger so i really couldnt help u out on this question.

 

There's no real difference with the sound. The difference will be in the pipe's opening, whether it be dual or single tipped. That's what BV was trying to say, I'm sure. The muffler will dictate the sound...it will muffle the sound via channels in the can. You also have to take into consideration the piping before the muffler, cat or no cat, cylinder compression. That all makes a difference.
...but in the end, it's all about looks. Do you want the stock look of dual tips or the aftermarket look with a single tip? The sound will all be in your head. As long as the total amount of gas that comes out of the end pipes are the same and the other variables are the same.