With the launch of "Mastered for iTunes" the guys at Apple wanted the most demanding people to have music with a quality very close to CD, something that Apple promoted in this way and which seems to be not the case.
The problem with these songs is that they still have compression that makes them lose details, so no matter how much they go up to 24-bit the quality is not close to that of the CD. The solution would be to use FLAC, which is lossless and is truly the audio itself.
Of course, one thing does not take away from the other: the songs from "Mastered for iTunes" really sound better than the normal ones, but unfortunately they do not meet the promised quality standards. Simply that.
Source | 9to5Mac
People who like to enjoy quality music, which I include myself, are forced to use alternative players, or plugins so that itunes directly supports flac, the problem is that what you buy in itunes does not give the size for nothing, and this rise to 24 bits is not a substantial improvement, it is a want and cannot. Like me, many of us use converters from flac, alac aac to apple losses, to minimize losses and obtain optimal results on iphone / ipad / ipodtouch.
I do not understand it, if we are paying for a music service, they should offer at least the same quality that a CD offers, in short to convert or compress to 164 or 196 it is always on time, but if I buy an album, I prefer to have it in original, because it allows me to extract it with quality and it costs me the same.