When comparing Krusader vs nnn, the Slant community recommends nnn for most people. In the question“What are the best file managers for UNIX-like systems?” nnn is ranked 1st while Krusader is ranked 9th.
Specs
Ranked in these QuestionsQuestion Ranking
Pros
Pro Great two-pane interface
Pro Folder synchronization
Pro Handles most archives. There is little difference in behaviour between an archive file and a regular folder.
Pro Virtual file systems
Search results as example saved into virtual folder and can be accessed later. All file operations may be performed on items in search results as if they were files in single folder.
Pro All common operations can be done with keyboard efficiently
In addition, shortcuts can be easily renamed.
Unlike Dolphin and many others.
Pro SFTP support
Pro Many operations like copying and moving files can be queued
Long running operations can be queued.
There is no point in doing them in a parallel way, as speed decreases dramatically.
Pro Can view and edit many files
Even editing a file inside a .zip file.
Has hexadecimal viewer embedded for binary files.
Pro Filename association and instant console availability
Pro Multi-rename tool
Pro Searching capabilities and copying/deleting/moving in background
Pro Custom commands can be added to the menu easily
And they can use the current folder, the selected files....
Pro Superfast
Pro Rich set of plugins
Pro Extremely lightweight (120 kb)
Pro Unique navigate-as-you-type mode
Pro Awesome new features being added in every release
Pro Minimal configuration with sane defaults
Default options and navigation is simple to grasp.
Pro Has a great wiki
Pro Sessions
Save and resume sessions.
Pro Supports cd-on-quit
Allows for quick switching between nnn and the terminal.
Pro Previews
The file manager has recently added support for preview hovered files using various methods.
Pro Integrates with the desktop environment and opens files in the default applications
Pro Reasonably well-documented
However, it requires some prior knowledge of inner workings of Linux and there are no tutorials (yet). NNN author is making up for this by actively responding to GitHub issues.
Pro Customizable icons and colors
Cons
Con KDE dependencies
If you don't use KDE, you'll be forced to install quite a large amount of KDE libraries.
Con New releases are infrequent
It can be seen in https://quickgit.kde.org/?p=krusader.git that maintenance work is done in a continous fashion, but no new releases are provided.
Even though it is perhaps the more feature-rich file manager.