In other words, it depends what you want. Some just care about sound, some a power increase, maybe both. There are unfortunately not a lot of A) Reliable dyno tests to show power differences side by side from the choices available. B) noise sample videos/charts.
I have the Yosh R77. Their dyno chart shows very similar power gains to the Graves, the only other dyno chart I've seen, but they could both be marketing nonsense. People here have done dyno runs but there was no stock run done so who knows if Yamahas advertised numbers are accurate.
As for the sound, I really liked the Yosh but it eventually became tiring for my old ears in the rpm zones I'm typically riding in so I installed the DB Killer. Much better for my taste.