Which bike you will go faster on is the one you are most comfortable with regardless of year, design, or horsepower ratings. Going faster isn't about twisting the throttle harder. It's about how the bike handles with YOU riding it. That differs greatly from person to person. What Rossi likes and what you can handle are probably much different. I always hate to bring this up, but Keith Code related that his students were stuck at the same speeds for many years even after the technology advances in tires, chassis, and suspension should have had them going 2 seconds faster per lap. So, to answer your question about which one I would do better on, is I would probably be exactly the same on both. This would be especially true on a tight course, where the HP advantage would never show it's face.