I dont understand that ?
Smal wing, small fins - can be much harder to ride, but also much faster/less drag (generally speaking that is).
In lower wind, you need a bigger or more lifting foil for max vmg upwind though, which outweighs the downwind disadvantage (which might not be there as you can go deeper).
So the foil has to be set up to your weight and the conditions, in able to be fastest on a track.
Being easy or not, does not matter as much if you get a significant advantage - as it seems the best still manages to handle it
James says it very well - that most on this forum will not be able to find out if a foil is competitive, as there are very few riders who can.