Bushmaster is a trained martial artist, so he probably has much greater maneuverability than the Beast. However, the Beast does have some pretty good strength and durability feats under his belt. I would wonder if the Nightshade enhancement does let Bushmaster overpower the Beast though. That said, the Beast is much more ferocious and bestial and more likely to want to punch in Bushmaster's face. Very tough to decide for me.
@ganon15: Possibly, but I think it's predicated on Bushmaster not getting hit. Bushmaster is likely faster and more maneuverable, but I think the Beast has a higher pain threshold, is more feral in behavioral terms, and probably can hit harder. He's also probably going to want to kill Bushmaster more than Bushmaster might want to kill him. That could even out any advantage Bushmaster might have in martial arts and consuming Nightshade.