Speed difference in two of the same boats is minute. Not measurable. Conditions in real world testing are too variable. You can line two boats up but there are always small differences in wind, waves, set up and skippers between the two. One will be faster for those reasons. You can try to figure it out, blame it on the boat etc. but if you boat speed is close tactics and boat handling will win in a race. Luck helps but not every time.