What type of harness is preferred for kitesurfing racing ? and why?
I have never really seen anyone using a waist harness for racing.
And would also use/uses a seat myself, unless I am out on a waveboard and the wind drops so I change to the raceboard just for being able to have more fun out there for longer.
The opposite also happens - out on a raceboard with a seat, and the wind and waves pick up and I change to waveriding with a seat - works awesome too actually, when used to it.
As I have said before - ups and downs for both types of harness in waveriding although waist often preferred, but for racing I see no advantages at all with a waist
Seat because you have better leverage - able to push the board harder - able to lean more "out", or "in", able to control heavy loads for longer time.
Besides the obvious power/trim advantage