Hi Dallas. One thing you always have to remember about bike stuff generally, and exhaust specifically; is that the choices can sometimes be very very personal. Almost religous.
Personally, I just happen to prefer true duals because I like having the area of the crossover pipe not covered up by the crossover. I like the look of having it open. I know a 2-1 might perform slightly better. I just don't care. I personally choose the look over the performance in that case.
For others the choices, and the reasons for them, are entirely different. The pipes you asked about are well advertised. They are commonly known. They have a "reputation" for doing a good job. Many like the sound. I personally don't care for them. But that's irrelevant to those that do; and it should be.
Of course the pipes also have a reputation for the things you pointed out as well. But it's bike parts. So the most important reason why they get bought is, most commonly, because that's what the guy with his name on the title wanted. And, whether I'd make the same choice or not, that's a perfectly good reason for the guy that wants them [smiley=xyxthumbs.gif]