BotanyBay said:9% on a powertap-generated graph / chart looks really significant, but how does that 9% actually translate into the guy rocketing away from you in a race? That's something else entirely.
I didn't say 'rocket away' but I can think of a lot ways an extra 35W is a huge benefit when hammering away sustained at 380W at critical points in the race. It significantly changes your options. Does this really require an explanation?