Mastered for iTunes” is more than marketing hype. “Mastered for iTunes” means just that; mastered expressly for distribution on iTunes. This is important because when iTunes first arrived on the scene, the accepted practice was to take the same master created for CD and use that for iTunes. That approach is fine in many cases, but, many masters created between 2000 and 2010 are considered excessively “hot” (i.e. high gain). It has been proven that excessively hot masters create a lot of problems for lossy encoders such as Mp3, or the iTunes AAC format.
By purchasing a “Mastered for iTunes” release, you are buying a product that has been mastered and quality-tested for publication in iTunes. If you could compare a regular iTunes (from CD master) release and an MFiT release, listening on a high fidelity, full range sound system, you would notice improved clarity of transients and dynamics of the music with this new iTunes mastering format. The intent with MFiT, is if you had access to a 24-bit uncompressed master and compared it to the MFiT version, they should sound virtually identical to the majority of listeners.