Hair textures look good, beard textures do not.
- Where's the stubble?
- The beards are too neat with all the hairs being the exact same length. And the exact same color. Compared to the amazing texture of the face, the beards look fake.
I'd suggest looking at styles of real beards and seeing how the texture and length and color of the beard can change. Some hairs should be finer than others, but the biggest culprit is the color being the same.
Also, please, please, please add salt and pepper beards and hair.