I think #2 and #3 are spectacular. What makes them stand out from #1 and #4 (for me) is that the background is appropriate. What I mean is, whether you planned it or not, you have avoided unrequired b/g content (for lack of a better phrase), like the other photographer and crowd. Also the tree has soaked up much of the blown out sky, which can sometimes overpower a shot.
I have been concentrating alot on composure for my own sporting shots lately with a conscientious thought of how much will my b/g alter how good my shot could really be.
#3 is the best. Portrait works here, for the horse is vertically extended and the composure is well centered. I would clone out the arm of the guy on the far left and call it frameworthy! Nice work.