Wouter, here’s a little "maths" analogy for you to calculate that may shed some light on just one “small” area that makes one boat faster around any course, (or a distance race for that matter).
If one sailor completes each of his tacks consistently in the order of 5 seconds faster than a competitor (which is a very small difference in reality) over the duration of a race and does even better on his jibes, say 7 seconds, (which usually means that the faster sailor will also gain time as well on his acceleration out of the tacks and jibes and he will lose less speed going into them, but we won’t include a theoretical figure for that) how many tacks and jibes would he have to make over a given time (you pick a “race” time) to give him a 2.5% advantage for the duration of the race? (Disregarding any other variables between the two).