Wind up is as accurate as wind down. Speed is irrelevent - it's the same vector triangle
The advantage of wind up is that for the most common problem - find HDG & GS given W/V & TAS/TRK - the jiggling of the compass ring is eliminated. The disadvantage is that it's a bit of a one-trick pony. If you wish to use the data for other problems you have to redraw using the wind down method.
Still, if all you wish to do is obtain HDG & GS and wish to save a little bit of mucking around, use the wind up. If you have trouble remembering which method to use for which problem, stick to wind down.
Or give slide types the flick & use a CR type instead and avoid the whole argument while gaining something that is smaller & more convenient without sacrificing accuracy...
