The character on the left has too prominent cheekbones and a thick, disproportionate nose; it offsets the rest of his features. I really like his hair, but I don't know why it is jumbled at the top, it would look much better if it remained flat.
I love the expression on the girl's face and all of her features. Her peering eyes and smirk really add a nice touch to her overall look. Her hair is perfect, though her collarbones look peculiarly fraud.
I would like to see an updated version of this, with more detail and better facial proportions. Good luck, Simply.