I think the last one worked best, The full on shots of the dogs head lose out because of the very dark muzzle. The last one, with the dogs features in profile has that something extra though a slighly less severe crop on the dogs rear may have improved the shot.
In the second picture, the woman (presumably the owner) appears to be making the dog lean to it's right which had me tilting my head slightly and the third is spoiled by the rat next to it. (I hate small dogs) 
In all of them though, the colour looks very natural and true to life.
The main thing is that the customer likes the photo's. Their opinion is really the one that counts.