On a 3x3 both would be ok, not so much on a 3x4-4x4.. PTO clutches are not heavy enough for the bigger balers.  I run 8xxxs on my 3x4 balers so I have enough "dog to keep the tail from wagging it too much".   I set the tires out to 102" centers on the fronts & the backs where the distance between is the same as fronts so I don't run over more hay than needed. I would go 120" on fronts, but my trailer necks are 102" wide & I like at least 1/2 the tire on.