I'm only going to give you my thoughts on the screaming Eagle because I bought it shortly after I got my bike. It seems to me that you can hear better when you're shifting or when you are in a gear and the bike is really working too hard in that gear than you could with the stock muffler. Of course being and long time rider I go by feel more than sound but you now can hear it a lot better than you could with the stock muffler.
It also seems to have a little more pep when you're starting out but then again this could be a placebo mind thing.
