VLC is nice as it plays everything and is very customizable as far as filters, codecs, outputs, and decoders go. It is not however an all inclusive suite of seamless media. Its beauty is in its simplicity and its bare bones handling of media.
XBMC is what I use for all of my HTPC's and the new version that is currently in RC2 is fantastic as it uses the new Audioengine for the backend, which supports 24/192 and all the HD audio formats (DTSHD, DD TrueHD, ect). It also offers control from virtually any smartphone or tablet on the market. So if you are running an HTPC you can ditch the mouse and keyboard and use a more convenient control solution. If you are actually using the PC for multitasking though XBMC is a poor choice when compared to a dedicated music player.
For music playback in a workstation/multitasking setting I would suggest foobar2000. I use it exclusively when sitting at my desk.
Not sure what your setup is but you have several options each of which should have equal audio quality, it will be what functions for you best that you should chose.