I really like this piece, proportions look very lovely. There are a few things that stand out to me: - The mane comes too far down and too close to the back. it should end higher up. - The face is larger than the body in proportion. the shape sholuld be more rounded and circular. And genereally in more proportion. - Another thing would be that the tail looks to dead. (Straight) Tails are folowing and should be going in all directions. Especially in this pose the tail should be flowing alot due to the wind from the horses speed.
Other wise this is a lovely line art. I think its amazing. Hope you win.