Not much to work with when it comes to the composition of the photo. However the first crop you made seems to be more dynamic even with the barren composition, thus, in my opinion, makes it the most successful.
I think what makes the first crop successful is the fact that the dog is looking towards the right side of the composition which kind of activates the, pretty much, empty space. (I was going to say negative space, but that isn't necessarily true) The other two crops are too centered which creates a boring composition.