I would think that the drinking water would be better. They say that drinking water is more healthy for humans to drink because of the minerals that distilled water doesn't have. Of course, if its better for us then i assume that it would be the same for the deer. That being said we just use our well water even though I personally do not drink it. It is safe to drink but the taste is not very good. The deer have to drink well water when they get to the pens so I think why not start them on it. Also, for us using distilled water would cost just as much as the milk powder so its just not feasible for us.