They are not gaining more power by having the dual exhaust system. The main idea behind the system is to create a quiter running bike. With all of the new sound issues and restrictions and with the allowed db level continuing to decrease at the pro level (AMA and FIM) as well as local tracks and trails, the manufactureres are looking for ways to maintain power output yet still quiet the bike down. In order to make the single exhaust system as quiet as the dual exhaust they would have to be much more restrictive and therefore cost themselves power for sound. Honda claims that the bike is more balanced now with the dual exhaust and it improves handling. I would say that it is negligible in that respect and doubtful that it is noticeable at all. But the benefits of lower sound are definitely there and because there are two silencers they are smaller which allows them to tuck behind the plate better leaving them less open for damage as they dont stick out as far as the single silencer designs. As far as weight goes, while it is slightly heavier it is not that significant of a difference since the two silencers are smaller and it is very balanced.