I'm up with the first one because I love the facial expressions on your son and his dog. I was wondering if a crop to lose some of the top area would bring it out more? Just a thought. The second one is too centered for my taste and because I cant see the boys face I fail to get as involved with the image
The first... your son's "there" for the photo. And the lighting is nice.
I am not sure about the amount of headroom you gave him ... it is not needed for the composition of this first photo here, less even since he does not look into that space but out of the frame, anyway. So a crop might even help the pic.
(Makes me wonder whether our mysterious Scribe would deem this one a real and true portrait? I would - this sentence spoken in brackets refers to an ongoing discussion on what constitutes a portrait in the Photographic Discussions forum).