All nice dogs and well captured. In my experience black dogs are MURDER in terms of a good shot. We occasionally look after a Golden Retriever and Black Labrador while their owners have a holiday. The latter is a great dog but I haven't got her right yet.
You're absolutely right. Especially with a snow background! This one turned out ok, but I'll bet I have another 50 that are either not black enough, or there's no detail on him. One of these years I'll get the definitive picture of him. Hopefully before he starts to turn grey. I have an idea of using a fill flash to get some glint in his eyes.