These two were done a significant period of time apart from each other.  The top one was the initial concept, which was just… rather stilted and awkward.  I came back almost a year later and drew the second, wherein their hair turned into a mane.  I did eventually drop the mane idea, and their ears grew a little shorter and rounder, but I was much happier with the design of the second one, especially its face and the placement of the horns.