Agree with all the other comments, especially FB's regarding wind up/down.
Wind up is fine for PPL. It's very slightly easier, but shouldn't be any more or less accurate. But it's no use for the ATPL exams, because there are lots of things you can't do with it.
My instructor taught all his studends wind down, which I was very pleased about when, over a year after first learning to use the CRP1, I decided to start the ATPL exams. If you're about to start using the CRP1, use wind down. If you've already learnt wind up, then don't bother changing if you're not planning on doing the ATPL exams.
The CRP1 is not designed to be 100% accurate. After all, the wind forecasts aren't 100% accurate anyway, even if you can fly to within 1kt and 1 degree. It's designed to give you answers that are as close as you need them to be, and any multi-choice answers should be sufficiently well spread.
Good luck!
FFF
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