qmmp vs cmus

Qmmp allows the user to drastically change its look via skins. It can use Winamp and Xmms skins, as well as a list of 12 skins made specifically for qmmp that can be found here.

Unlike more popular players that draw a huge window taking up the entire screen, with tons of knobs and menus popping out in new windows, qmmp gives you a single tiny window (that looks pretty much the same as Winamp used to look) with the basic controls and the playlist. The rest is available through a menu.

You can extend it with plugins.

No matter what OS or desktop you use Qmmp will integrate well

It depends on libaries instead of big fat toolkits like gstreamer.

CLI makes Cmus clean, fast and minimalist.

Cmus only uses about 15 MB. This is a very small and light media player, which is ideal for people with low end hardware.

cmus will factor in additional data from the MusicBrainz database while sorting. For example sort orders for arist or album, and the original release date for an album (in the case of a re-release).

A lot of music players may act more like playlist viewers rather than a music library. cmus sorts by Artist > Year > Album.

A lot of music players will be slow when starting if they have huge libraries, but CMus starts fast no matter the library size.

You can add keybindings for just about anything - including seeking (forward/backwards 1 minute, for example) which isn't supported by all music players.

cmus does not require a mouse as it runs in the terminal

On GitHub you can find the official WIKI where there are a dozen extensions and scripts from color themes to a lyrics viewer and the ability to play YouTube songs.