I like the dog best, then the owl and last the mare. Why? because to me it's not about accuracy, but whether or not the drawing has "punch" and "feel".
When I see the dog, the drawing is brave in it's use of texture and dark/light contrast and there is character in the dog's face.
The owl , had strong attration to the eyes and it's offset placement on the page is also attractive. It would be lovely with the faintest hint of color from color pencils.
The mare is pretty stylized and , to me, somewhat impersonal. I cannot say why. Maybe it's that everything on her is treated with a softness , except for the eye, which is really nicely done, the rest of it just doesnt' have "punch".
The ears are too small and they don't come out of the poll area quite right. They narrow down a lot at the point where they leave the body.
The muzzle is beautifully rendered, though the head feels a bit long overall.
You are just working on getting back up to speed. Don't fall in love with any drawing, do it, enjoy it a bit and move on to a new one. Every "ride" makes a better rider.