Like Wouter said, you really need to swap boats and see if anything changes. It will, no doubt, there are no two sailors who are identical even if the boats are, there are fast guys and not so fast guys, and in certain conditions, some guys are fast, and in other wind, not so fast.

I did this a long time ago when a group of us were all sailing "one design" Nacra 5.5's. I got on the "champion's boat" and it felt like a completely different boat, it felt lighter, faster, flew a hull quicker, etc, yet we all had Nacra 5.5's. We even measured the sails, pretty much the exact same size, but all his stuff was -brand new- and all my stuff was 5+ years old. It makes a huge difference.

I'm sure your two boats are both new, but still you should try his boat and he should try yours, see how they feel.