When comparing gmusicbrowser vs MPlayer, the Slant community recommends gmusicbrowser for most people. In the question“What are the best audio players for UNIX-like systems?” gmusicbrowser is ranked 19th while MPlayer is ranked 43rd. The most important reason people chose gmusicbrowser is:
This program uses a tagging system to help you find the music you're looking for, and can even help find duplicates. It will also automatically sync with a folder, meaning you don't have to manually initiate a scan.
Specs
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Pros
Pro Great with large libraries
This program uses a tagging system to help you find the music you're looking for, and can even help find duplicates. It will also automatically sync with a folder, meaning you don't have to manually initiate a scan.
Pro Cool AutoTagger
The smartest auto tagger out there. It has an intelligent regular expression system to tag the files based on the filename contents. If the name contains something like Band -Album - Track -Title www.download.mp3, the system lets you filter the metadata fields.
Pro Large assortment of layouts
You can pretty much emulate your favorite media player layout inside of gmusicbrowser as it has a large assortment of pre-made layouts as well as an insurmountable amount of options for custom layouts.
Pro Remembers playing/pause status even after restart
With most other options, you have to start the player, wait a few seconds, then click Play. Gmusicbrowser spares you the wait and plays music automatically upon startup (if you were playing music when you closed it previously).
Pro Intelligent auto playlists
Automatically generated playlists with the criteria you decide. Great for big collections.
Pro Needs no additional codecs
Everything MPlayer needs to play media files is contained within which means no outside codecs are needed.
Pro Easy shortcut keys
Quick skip ahead buttons and other shortcut keys.
Pro No bugs , no lag in the video display
Pro Works via CLI and has multiple frontends to choose from
Some of the more popular frontends include Deepin Media Player, GNOME MPlayer, KPlayer, KMPlayer, Rosa Media Player, SMPlayer and Xt7-Player.
Pro Nice theme available to choose from
Also, the video window is separate from the main window making it less cluttered while playing audio
Cons
Con It won't install on Linux Mint 21
Con Held back by performance issues
Can be very slow, uses a lot of resources, and has a decent amount of lag when going between songs.
Con Doesn't support media keys
Con Unusual keyboard shortcuts
Space does not pause, for instance. This would have been useful, as hitting the space bar is easier than finding the play/pause button - most music players use the space bar in this fashion.
Con Some plugins are outdated
Several plugins works on older versions of libraries no longer available for recent distros.

Con Poor library management
Initial load may have issue skipping parts of ones library, re-scanning may not resolved the issue. It also may tax ones CPU quite a lot, during these load attempts.
Con No WMA support
For those with older libraries that may still have unconverted WMA files, this can be a non-starter.
Con Large assortment of features and layouts may be confusing
Some people may find all of gmusicbrowsers layout and options daunting to figure out.
Con Not much documentation on the use and configuration
Con Contrary to review, some media that play well in vlc does not play in mplayer
Con Doesn't support directory playback
Con Lacks a built-in visualizer
