You're obviously asking in the wrong place, since the first few responses are way off. Mastered for iTunes establishes criteria that raise the standards of mp3s available on the iTunes store. It isn't just hype, it's a real thing. How different it sounds from the CDs depends on what master is used, though: for a while there MfiT was the only place you could get the new Led Zep remasters, but now obviously the available CDs match (or likely exceed) MfiT quality. It's not intended as a differentiator between CDs and mp3s though ... it's a differentiator between mp3s on the iTunes store and mp3s available from competitors.
I have decided to permanently step off of the digital bit-wars upgrade to infinity and beyond path. It's never going to end and I have had enough after 30 years.
If I could go back to just my vinyl LP collection, I would - but it's not possible where I am, total lack of vinyl sources and I sold them all 15 years ago.
So I will stick with FLAC rips of original pre-1983 vinyl and DSD at 5.3MgHz when otherwise played through the oldest thermionics that I can find and a great pair of cans.
Some pieces I owned on 8-track, cassette, original import vinyl, original domestic vinyl, repurchase of the domestic vinyl (wore it out), original domestic CD, remastered domestic CD, re-remastered domestic CD, Box Set #'s 1, 2, 3 and 4, and now the 192/384 uploads are coming and next will be the 5 3MgHZ DSD. Over one dozen versions of one album.
Enough already.
The original import vinyl was superior and still is. England, Japan, Germany if you can find them.