When comparing GNOME Files (Nautilus) vs Thunar, the Slant community recommends Thunar for most people. In the question“What are the best file managers for UNIX-like systems?” Thunar is ranked 2nd while GNOME Files (Nautilus) is ranked 17th. The most important reason people chose Thunar is:
Unlike Nautilus, which requires the whole GNOME desktop, thunar just depends on some XFCE utilities & GTK.
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Pros
Pro Minimalistic looking
It does what it is supposed to do, and leaves a lot of screen space to look for a file.
Pro Widely supported
The program is distributed as a single source archive, which can be configured, compiled and installed on almost any Linux flavor. There are no binary files for a specific Linux distribution, but you can install it directly from the default software channels of your operating system.
Pro Easy to use and familiar user interface for Ubuntu users
The user interface of Files is very familiar to Ubuntu users, most probably because Canonical still uses Nautilus (an old version of it) as the default file manager for its world’s most popular free operating system, Ubuntu Linux.
It split into two parts, a sidebar and the main file viewer. While you already know what the latter can do for you, the sidebar offers quick access to Places, Devices and Network locations, as well as any other bookmarks that you can add whenever you want.
Pro Allows you to access remote or local locations
On recent versions of GNOME, you can click the Files entry in the panel to access a specific location (remote or local), connect to a certain server (FTP, SFTP, SAMBA, etc.), access your bookmarks, open a new window, as well as to change its default functionality.
Pro Quick file preview
GNOME-sushi allows you to quickly view files without opening them. It supports most audio and video formats, but support for more can be added.
Pro Wayland-native
Can run under Wayland without XWayland.
Pro Supports natural sorting (not on all distros)
Dolphin, Deepin File Manager and Pantheon Files support this, too.
Pro Nautilus action configuration tool can configure systems in ways no other FM can
It can configure popup menu depending on file type.

Pro Minimal dependencies
Unlike Nautilus, which requires the whole GNOME desktop, thunar just depends on some XFCE utilities & GTK.

Pro Supports "quick-directory" typing
While in a Thunar window, typing either a "~" or a "/" will automatically start typing into the "address-bar" and pressing enter goes straight to the typed directory.

Pro Non-recursive find
In a thunar window, any non-directory typing will search in the current directory for the filename that you type (non-recursive, unlike Nautilus)
Pro Select by Pattern
Select multiple files in the current folder using a wildcard pattern.
Pro Custom actions are easy to set up
Use Custom Actions to add right-click options to do things like Open as Root, Open Git GUI, etc. You can filter the file types and filename patterns that the actions will show up for.
To add an "Open as Root" action, go to Edit, Configure custom actions. Assign a name and a description. Set Command as "gksudo xdg-open %f" (you'll need to install gksudo since pkexec won't work). Pick an icon (I prefer "changes-allow"). Under Appearance Conditions, select Directories, Text Files, and Other Files.

Pro Supports forward/back mouse buttons
Supports the M4 and M5 mouse buttons for forward/back, similarly to most browsers.
Pro Supports renaming files in bulk
With also predefined functions as insert (date, numbering,...), search/replace, etc ...
Pro Split View
Browse files in two directories with a dual pane view.
Pro Does the job
But nothing more.
Pro Keypress to search in folder
While in a Thunar window, typing a filename automatically selects the first matching file in the current folder.
Pro Can assign custom shortcuts to scripts in XFCE
Thunar can use the editable accelerator feature of XFCE.
Run xfce4-appearance-settings
in terminal, go to settings tab, check "enable editable accelerator". Now open any command in Thunar menu, hover to a command, i.e. your custom "places" or your custom command, then press any combination to assign a shortcut to it.
be careful though, cause it will also remove the shortcut from other command.
Pro Tabs
Use tabs to open fewer windows. New tabs automatically start in the same location. Tabs can be detached.
Cons
Con It has lost so much functionality
As already stated, this is not well configurable anymore. One can not even start in dual pane mode for cut/copy and paste. Just a ridiculous transgression. It was great just 1-2 years ago, but over-simplification in this case is detrimental to functionality.
Con Mostly unconfigurable
There are not many ways to configure Nautilus to fit your needs. Besides what can be seen in the settings button you can't configure it further.
Con Outdated
It is not updated frequently and Ubuntu could stop using Nautilus and switch to Nemo.
Con Awful date modified column.
It should list by full year month day, no matter whether it was today, last month or years ago. Displays wrong time modified for photos I took and downloaded today (not exif time taken and not anything that makes sense). Not customizable in any way one would expect.
Con Has/had memory leaks
Sometimes about 600MB of RAM goes somewhere...
Con Forces you to constantly swap between mouse and keyboard
Con Slow at moving picture folders
A move, even to the same disk, can take a minute for a folder containing a hundred images.
Con Can't right click in list view mode with a long file list
If the file list is long enough to fill the screen, then there is no empty place to click for bringing the context menu. Need to change the view to Grid view, then right click.
Con Still does not remember per folder view
This is the last missing feature that was removed long time ago and makes Nemo competitive. Should be reimplemented remembering view type and icon size folder by folder.
Con Creating sub-folders within full folders is not possible anymore.
In order to create a new folder within another folder that is full to the bottom of the page, we must create a folder in an open area somewhere else, then move the sub-folder into that full folder. Even worse, we need to use the "Move to..." option, with so many extra clicks, instead of just being able to copy and paste as before.
Con "+ Other Locations" is a stupid change
"+ Other Locations" in the left pane now forces us to click twice or more in order to access additional drives, even the local "Computer." Having all of the drives listed on the left side was quick and easy, and the drive "Properties" were available just by right clicking once, although drive "Properties" is no longer available when clicking on "+ Other Locations," then right clicking on the drives.
I still use Debian 8 for the older Nautilus, even though the developers already damaged that older version as well. However, Nautilus is completely useless to me now in Debian 10 so I am seeking for a new graphical desktop to replace Gnome and Nautilus...I am fed up with the developers.
Con Has too many bugs
There are too many bugs at the current state for this file browser to be usable.
Con No integrated search option
Con No usable image view mode
Setting view to "icons" doesn't satisfy. The icons are too small to see the image.
Con Simplified action bar
The action bar on Thunar is very simple and doesn't have as many features and buttons as other file managers. It only has a back, forward, up, and home buttons as well as the folder path.
Con Does not integrate well into Gnome
Con Tree sidepane missing features
When the sidepane is in Tree mode, it does not show Places (Favorites). It also doesn't collapse folders (like Windows Explorer), adding to clutter.
Con Requires GNOME dependencies to support common features
Thunar relies on GVFS to support mounting disks or accessing web folders, however since GVFS is a third party GNOME library and made for the use in the GNOME environment its often incompatible to Thunar stable releases which results into crashes and other issues
Con No double pane support
Working all in all quite good out of the box, but the windows are too big. Drag & drop is working, but useless on a one-window file manager. Even for novice users it's too weak for everyday work.
Con Requires plugins for some basic functions of modern file managers
Con No Split View without a patch
Which can be a deal breaker.
Con Moving files
Has serious problems moving files. It may stop abruptly with some undefined error message and the files would be gone afterwards.
Con Won't write to any removable media that has been on an Apple machine
Removing dot-files that Apple puts on the media (like .fseversd) allows Thunar to write to it.
Con Doesn't integrate well with archive manager other than Xarchiver
"Extract here" function doesn't integrate well with archive manager other than Xarchiver (e.g. Ark, GNOME Archive Manager).
Con Image thumbnails sometimes wrong
There seems to be a bug where sometimes images get the wrong thumbnail, this can lead to data-loss.
Con Slightly unstable
Thunar crashes some times on file moves, copy-pasting etc. The developers are working on it, but it's taken a while.
Con No progress bar when copying/moving file
Either this is problem with XFCE4 or Thunar, but there's no progress bar when copying/moving file with Thunar.
The only way to tell whether it finished is CPU usage.
