I've done extensive switching back and forth between the two headphones, and there are some differences I can point out. HE560 likely have more extended bass, and slightly more decay, and therefore softer, but Sundara with harder, more responsive or quicker bass. HE560 is brighter up to in the lower treble, but the Sundara may come off a bit upper-mid lifted for some people sensitive to that area. Sundara sounds faster and sharper or snappier, but HE560 sounds a bit more defined tonally for sounds with better defintion. Therefore, HE560 sounds more refined. Both have slight dip in the mids, but Sundara sounds like there is more of a cut and perhaps more noticeable due to upper-mids being enhanced with it.