F18 Spi Nylon or Polyester

Could anybody please describe me the difference ? Performance ? durability ?

Price of the polyester a bit higher, is it worth a few extra € / $ ?

Nylon stretches badly.

I didn't think anyone was making nylon sails anymore because of that.

standard at Nacra...

Contender Superkote 75,80,90 are all Nylon Standard use for most F-18 Spinnakers. All but one approved sail material is Nylon or Nylon Silicone or coated Nylon.

the only approved polyester spin material is
Dimension Polyant 7722UCP/6611UCP,in Australia

Mike and tripp have a polyester spin from performance they got at worlds last year. They used it at nas and Canadians where they were lighting fast downwind. They swear by it and say that it feels much better off the wind. Tripp said the tug is amazing compared to the other.chutes he's used. But the downside is you can't use it unwind in super light or tight reach with it.
I'd get one if I had the choice.
I've got to talk to tripp in a bit ill tell him to weigh in.

The coated nylon used in F18 kites stretches a little and is more forgiving of trimming errors. Nylon has better tear resistence than polyester. Polyester kites do not stretch as much, but are brittle and tear easily. Since polyester kites stretch less, they hold their shape better. Its a trade off between ease of use/durability and performance.

Thanks to All for the responses.

I got the news from the local Nacra dealer today the Performance finished producing the polyester kites. I don't knot is it a good news or a bad, anyway simplify the choosing process...