When comparing Double Commander vs One Commander, the Slant community recommends One Commander for most people. In the question“What are the best file managers for Windows?” One Commander is ranked 9th while Double Commander is ranked 10th. The most important reason people chose One Commander is:
Free for non commercial use.
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 Free
Free for non commercial use.
Pro Simple and fast
Fast search and filter.
Pro Miller columns
Like Finder from macOS.
Pro Multi tab support
Pro Themes
Light, dark and customizable themes/colours.
Pro Default file manager setup
Can make it the default file manager such that windows explorer stays out of the way for most of the work.
Pro File previews
Pro File / folder filters
Pro Folder views can be saved and applied
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 Folders cannot be sorted by size
Con Cannot access Android device connected by USB
Con Cannot access Android device by FTP
And can never will as this is clarified by developer that this feature will never be added.
Con It doesn't have UNDO function
Very important. When you work with valuable data files, this function can't be ommited.
Con Navigating folders by Ctrl+Tab has considerable delay
Con Browsing Recycle Bin is very slow
Navigating away from Recycle Bin tab and coming back to it reload the Recycle Bin which is very slow as mentioned. Program has an option to open recycle bin in Windows File Explorer, which suggests that developer is aware that opening Recycle Bin is problematic.
Con Confusing
Con Context menu only based on icons
No longer with Onecommander 3.6.43
