I use the horizontal nipples and put the bucket on cinder block(s) to raise it up a bit to make it easier for them to drink. I can tell from the wet cinder block below the nipples that they are using it. Also, if some get it, all will because they watch and learn from each other..
Watering nipples are the way to go, and horizontal ones are better (IMO) than the vertical kind. I have both. Vertical nipples will freeze in the winter, but horizontal ones won't if you keep the water from freezing.