I think I'm not mistaking if I say that there's much more grass in The Witcher 3 than in Skyrim.
In Skyrim you see tufts of grass, in the Witcher 3, the ground is literaly covered in grass.
A not so fair screen comparison :
http://cdn.wccftech.com/wp-content/uploads/2015/05/Witcher-3-124.jpg...