Sort of an open ended reply on my part but I think it depends on what dog you are putting it on. For my last two dogs who where, and are very oily I ended up with a camo version of a small Gortex horse blanket that after they are out of the water and a shaken off most of the water I threw it over their head and back. Both dogs ended up staying much warmer than with the neoprene because they were not contending with the evaporating water that was trap in a traditional vest.
I came upon this by accident when we hunted a day that was in the single digits and the vest was freezing up. I pulled it off the dog and but my gortex shell over the dog, hood and all. She stayed warm as toast the rest of the hunt and that night I ordered her the horse/dog blanket thing and never put a vest on her again, except as protection from sticks early season in the beaver ponds.
Like us all dogs or different but it wouldn't hurt to try both and see which works better for your hunting partner. On a side note I think George W.'s old dog is big enough for a regular horse coat.