It looks like X doesn't have any hardware acceleration for forwarding. With 64b packets, X can only push 130k PPS while ERL should do at least 1M PPS. This doesn't matter in a home network though.
kornholi, do you have an ER X? If you do, I appreciate your first-hand information. If you don't, I asked mrbill the question that I asked because I was looking for his first-hand experience.