Yes, AIFF is not compressed; Apple Lossless is. Some still use AIFF in their iPod's for the chance of slightly higher fidelity (debatable, arguable, theoretical) or the mere fact that they don't want to carry/store multliple copies/formats and use AIFF for their home music server. My $.02 is that even if AIFF has slightly more fidelity than it's lossless counterpart, the iPod/headphone paradigm is not the best platform to discern this on....go for Apple Lossless or even lossy high bit rate AAC (not bad at all for travel).