I think a multi cross would last longer than a multi main because the poly main would rub along the multi. A poly cross would rub across the multi main. This would be magnified by a shaped poly cross. Somehow, this is not the case with a nat gut main. Something about the gut's oils acting as lubrication.
MuscleWeave 200G (348g 8.5 HL), Multifeel 1.25/Black Mamba 1.23, @52/46, dropweight stringer