Long side in all three cases of poly axle failures that I'm aware of and I'd bet there are more stories like ours. The first person that Slee Off Road talked to at poly said they were aware of the problem and then when Christo talked to the owner of poly, that person claimed that he was unaware of any problems.
It can be seen from the pic of my axle that the problem is consistent. Both of my poly axles were sent back for inspection and a new long side and the original short side were returned to me without any word as to what the problem was and the new long side didn't have the poly sticker installed on the hub side and looked as if it had been sitting on a shelf for a long time. Not very reassuring about its long-term worth but the OEM axles had already been sold to Ige so the polys were reinstalled. The first indication that the axle had gone south was diff lube running down the inside of the tire. So much for bullet-proofing the rear axle to match the Long-ed front axle.