Why is it the best??
Probably down to years of their research and development department.
It's what they do!
I've had my bike dyno'd a few times and the fella who does it, who i can only describe as a master wizard with race bikes, told me so, so whatever he says totally trumps me.
He said he's yet to see an aftermarket exhausted Fazer run better than a stock one!
Too quiet and irritatingly whiney for me, but i do still have it in the garage........and the exhaust as well.
But unfortunately the downpipes, along with a few other major parts, were made on the quick with materials that were as soft as shite and prone to decay, which is a real shame.
One day i might refit it and try it out for old times sake. (not really)