At first the M8 may give you the impression that it's got less clarity than a lot of other phones. Including Sony, Nexus5 or even the M7. However if you listen again, you may realize that it doesn't really lack clarity at all -- all the sound elements are well-reproduced and you will be able to easily distinguish the quality of different files (e.g. MP3 vs FLAC) or lesser versus better headphones.
The M8 is also better than most smartphones right now in its ability to drive certain headphones and IEMs. Its advantage may not be so obvious if your IEM is fairly easy to drive to a good volume, but with over-the-head headphones, or something a little less sensitive (or higher impedance), I think the M8 sounds fuller and more dynamic.
It's also a much more involving, fun sound than Sony's signature sound if you listen to rock or EDM.