To answer question directly: no rotation at all will give you "optimal" number of bad edges, as expected value is 6 for every orientation and any fixed rotation, on average, won't change anything. (Sometimes rotating will give you a better case than not rotating, sometimes it'll give you a worse case... these will balance out as sample size increases)
More interestingly, you can look at how advantageous it is to use 1 fixed front vs 2 fronts (e.g. y neutral) vs 3 (full neutral) assuming that you always pick the front with fewest number of bad edges. iirc you get severely diminishing returns and 3 almost provides no additional benefit