When comparing Gnome Music vs Lollypop, the Slant community recommends Lollypop for most people. In the question“What are the best audio players for UNIX-like systems?” Lollypop is ranked 12th while Gnome Music is ranked 37th. The most important reason people chose Lollypop is:
You can view all the albums you have in one long list. Clicking on one of them will bring a popup at the bottom of the screen where you will see a list of all the songs on that album.
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Pros
Pro Simple clean and minimal interface
Pro Open source
Pro UI design consistent with GNOME desktop environment
Gnome Music is GNOME's default music player. If you use GNOME Desktop Environment, you'll feel familiar with other GNOME Apps like this one.
Pro Stable
Pro System-wide music organizer
Gnome Music automatically seeks and organises your music files throughout your system using Tracker.
Pro Super intuitive way of organizing and browsing albums and artists
You can view all the albums you have in one long list. Clicking on one of them will bring a popup at the bottom of the screen where you will see a list of all the songs on that album.
Pro Works fast and reliably
Pro Super flexible layout
The latest version has a good full-screen layout and is very responsive. Goes very smoothly from full screen to minimal player (also being a GTK+ app).
Pro Integrates with the MPRIS sound menu
This applies for most players in the "Linux world", but not for all. Therefore I consider it worth mentioning.
Pro Huge development
There is constant improvements, librem and gnome3 is possibly the future.

Pro Cloud music
Lollypop allow you to play music from the web (iTunes charts and search from Spotify).
Pro Integrates well with many desktop environments
One example being the conditional use of client side decorations (a.k.a. header bars) depending on the currently active desktop environment.
Pro Good party mode
Pro Clean, light and works very well.
The only one that can play a lot of files without to stop.
Pro Queue option lets you change what's playing on the fly
You can add songs to a queue, and then re-order or remove songs as you please. It works similarly to a temporary playlist.
Pro Online radio integration
The newest version features a nice interface for adding, browsing, and playing online radio stations. This gives you access to more music than you would normally have, which can help expand your music library for free.
Cons
Con Cannot change library folder
Con Too Simplistic
It works as a simple music player with a GNOME look, but it has very few features and almost no configuration options. Too bad.
Con Buggy
Gnome Music needs a tracker daemon running in the background and that thing never loads the music. It takes forever for a huge library to be loaded even if it was previously partially loaded.
Con GTK App
Its a GTK app so integration in other desktops is terrible it also uses GNOMEs ClientSideDecorations so it will break many window managers.
Con No equalizer
Lollypop still does not have an equalizer.
Con Good party mode
Con No In-App Volume Control (0.9.242)
It has no in-app volume control, it has to be managed through system 'Sound control/Applications'

Con Requires a well organized music collection
Lollypop will be a pain to use if music is badly tagged. The setup is a one time thing, but it can be a pain to organize a large library.
