You are sailing in a one-design fleet.

Your sail trim is good, your crew coordination
is fine, your boat bottom is clean and perfect.

You are following the fastest boat in the fleet,
pointing as well, and factors like crew weight
and position are the same. Sail trim looks
identical between the two boats.

But the other boat has consistent better speed
upwind, while you have similar speed downwind.

What factors might be making the other boat faster?