The Agera R when running on Biofuel is faster than the Agera S, but when they are both on low octane gas the Agera S produces more power.
I've heard from somewhere that next year they are planning a race between a Bugatti Veyron SS, Koenigsegg Agera R and McLaren P1 but I'm not sure if that's true. If it is I don't think the P1 stands a chance although it might surprise me.
An interesting video but could have guessed the outcomes.