If there was only one type that was the best, then only one type would be made and used. Not so simple. Different degrees of shading are necessary in different climates. Also different degrees of shading are necessary at different stages of growth. Generally plants need the most shade when they are very small, then amount of shading can be slowly reduced, until they go full sun. I use 3 different shadecloths in shadehouse (80, 63, and 50%) and move plants to lesser shade as they get older. In extremely hot climates as much as 80% shading may be necessary in the beginning. In very cloudy areas, or time of year when it's very cloudy, no shading at all will be necessary. So really you need to experiment a bit to see what works best for you at your place.