I think a lot of the value of the various types of exhaust is determined also by the type of riding. If I were to ride with a bunch of other KTM 9XX riders, I'd want to look like I was knowledgeable. So my home made exhaust pipes from wine bottles wouldn't cut it. On the other hand, if I was perpetually out in the dez scratching and fighting my way up hills and down dales (shhhh, don't tell her I said that), then I'd probably want FMF's or something else not quite as blingy/pricey when they got dinged and scratched. Oh, yeah, I know, "don't drop it." How many times have I heard that. War wounds and battle scars is what I called them on the VStrom, CRF450X, and WR250R.
I like the idea of a multiple rating system, but then again, it still wouldn't answer the bottom line question of "which exhaust is best...FOR ME?"
Keep em' rollin in.
2015 Triumph Tiger 800 XCx
2009 Harley Road Glide
2006 Buell Ulysses