In my opinion you can get pretty good looking results with ground materials. You just have to bring lot’s of variation in it -> take a look at the starter content grass material + add a overall normal map over all landscape textures (in the material editor)
You should paint a grass material onto parts with grass meshes, because when you e.g use a dirt material it wont looks so dense, because then you can clearly see the gaps between the meshes -> the density gets lost 