Buxus

really depends on maintenance, the factory finish is really good. Hardwood sills are better if the finish wears but otherwise it doesn't matter.
I have a friend who works for a joinery shop and they are pretty much exclusively using
accoya now.
If the painted protective surface is kept well, then it doesn't really matter

apologies for not replying I have been out of the country.
The windows from byng joinery are top quality. I have put them in loads of clients houses and just installed 9 throughout my own home.
Been using them for about ten years now and never had a problem with any of their products or service.
If you have any questions or want me to take some photos of mine just let me know.
Best wishes
Gareth