I can't talk to round bales, as they're rarely used here in central Nevada. You do see more of them up along the Humboldt River on ranches. Most of these round bales are meadow grass hay and they're often left in small piles in the pastures up away from the bottom areas. I always see these stacks made with the round bales on their round sides, never stacked more than three high.

But for small bales, there is definately a difference in how you stack the bottom tier of a squeeze block. If the lowest tier is "flat" -- ie, the wide side of the bale against the ground, they can suck up quite a bit of moisture out of the ground. The preferred way to stack hay now is with the "edge" of the bale against the ground. In large square bales, tho, they're always stacked flat, ie, the way they come out of the baler.