When comparing Double Commander vs PCManFM, the Slant community recommends Double Commander for most people. In the question“What are the best file managers for UNIX-like systems?” Double Commander is ranked 4th while PCManFM is ranked 10th. The most important reason people chose Double Commander is:
You can use same tool in all desktop OS environments.
Specs
Ranked in these QuestionsQuestion Ranking
Pros
Pro Multi-platform (Linux, Windows, MacOS X)
You can use same tool in all desktop OS environments.
Pro Source code is available (true free software)
If the developer loses interest there is at least the possibility that someone else will pick up the torch.
Pro Configurable
Lots of options allow you to configure DC the way it suits you best: Tools, Fonts, Colors, Hotkeys, Mouse, Fileviews, Plugins, Layout, Toolbars, Tabs, Icons etc.
Pro Directory Hotlist
Save shortcuts to folders. Organize them in a treeview with submenus. Define a name and sorting for each entry.
Pro Powerful tcmd-like search tool (alt+F7)
Pro tcmd-like multi-rename tool (CTRL+M)
Pro DC uses TCmd plugin API
so you can use documentation from Total Commander for writing plugins. WCX (packer), WDX (content), WFX (file system), WLX (lister).
Pro Closely follows TotalCommander UX
For instance, the 'Settings | Layout' pane is quasi-identical to TCs.
Pro Very sophisticated
Although it is lightweight and simple to use, it can do very sophisticated tasks, like copying files from directories which have a certain extension or file size or have a certain text pattern in them. Also, it's very customizable and stable.
Pro It's that good, you can replace tcmd on windows too
Pro Source code written in (Object) PASCAL
It's all a matter of perspective. I'm not for an argument about IDE's, frameworks etc, but to me that's a big plus. I think it should be a tie, it's either a pro or a con or should that be neither a pro nor a con. It just depends on context.
Pro Lightweight
General use, and most operations, are snappy and responsive.
Pro Simple
PCManFM is a very lightweight and simple file manager.
Pro Can open folder as root
PCManFM can open different folders as root, this way you don't have to use the terminal to move around files for which you need root permission.
Pro Auto mounts drives
PCmanFM automatically detects and mounts available drives.
Pro Supports "quick-directory" typing
While in a PCManFM window, typing either a "~" or a "/" will automatically start typing into the location bar, allows for tab completion, and pressing Enter goes straight to the typed directory.
Pro More RAM is available for other processes, and the system uses less swap
Overall, the system becomes faster.
Pro Uses tabs instead of new windows
Tabs can practically be managed just as in a browser, so you don't end up with windows open all over your desktop. New tabs automatically start in the same location.
Pro Fastest starup
PCmanFM is the fastest GUI file manager to start.
Pro No back seat driver
Does not obstruct professional work by engrossing root warnings.
Pro Compact
Supports fast failure resolving in bulky configuration and log folders.
Cons

Con Apparently only one developer
Con Freeze after mouse double-click on directory list item
Con Much slower on Linux and Mac than on Windows
Con Source code written in Pascal language
But this does not affect users negatively. It's just programmers problem.
Con Not developed anymore for Mac
Con Can't edit files on remote FTP servers
Con Can't extend with scripts
Unlike Nautilus and Caja, this can't extend with scripts. If script extension is added it can become a really good FM.
Con Some operations are slow
Because it tries to be as lightweight as possible and tries to use very little RAM. This can unfortunately lead to it being slow sometimes.
Con Right-click option choice limitation
You can only choose one option in the right-click menu instead of being able to select multiple at once.
Con Uses a bit more RAM than thunar
Thunar uses less RAM but you pay in slower startup and stability.
Con Directory trees can be confusing
Starts you off in a directory tree that is your home folder as if that is the very top. (Just use a single tree as it actually is and expand appropriately).
