I have both E-W and N-S rows of wrapped bales. I don't see a big difference between compass direction. What I do see is rows running up-down hill hold up better than level or across the slope, obviously due to water drainage.

Another issue here is holes in the plastic, mostly on top of the row, caused by birds and other wildlife. Holes on top seem to cause some mold on the outside of the bale which can be removed by unrolling all or part of the bale.

I find moisture entering from the bottom due to the wrapped row sitting in wet areas tends to cause mold throughout the bale. Insufficient number of wraps will do the same but even well wrapped bales will mold if sitting in water.