When comparing XnView vs Gwenview, the Slant community recommends XnView for most people. In the question“What are the best FOSS image viewers for UNIX-like systems?” XnView is ranked 5th while Gwenview is ranked 11th.
Ranked in these QuestionsQuestion Ranking
Pros
Pro Supports over 500 image formats
Pro Includes simple editing tools
Typical image editing tools are included. For instance, there are tools for color and size manipulation, several filters and effects.
Pro Available for macOS, Linux and Windows
Pro Easy redate and view configuration
Pro Compare images side-by-side
To delete blurry phone pics, etc.
Pro Multi-lingual
XnView speaks over 30 languages.
Pro Portable version for Windows available
Pro Easy to navigate folders
Pro Quickly view image metadata
Pro Easily resize, crop, flip and rotate
Pro Keyboard shortcuts can be redefined
Pro Images can be sorted by name, date and size
Cons
Con Very poor quality and very invazive on windows 10
Convert all images to 8bit rgb
[not suport 16bit or 32bit, cmyk, Lab, multichannel] so you never be able to see real original image, you only see the result of conversion...on windows 10 it enforced self promotion to default app for every type/format of image...
Con No Dark mode
Con No custom installation - if you need i.e. a language package, you need to install the full version
Con Free only for private use
For use in a company 1 license starts at 26 EUR.
Con Doesn't show movies on phone in correct position
Some of mp4 files shows in upside down position.
Con Doesn't pan/zoom fluidly with touchscreen
Con Has a bug that causes certain png files to show brighter than normal
The image, if is a png that contains gamma information, will appear washed out. There is still an open ticket concerning this issue.
Con Very slow on remote folders
Compared to others, like XNview, is VERY slow when retrieving images from shared folders (NFS or Samba).
Con Not lightweight
Needs a lot of KDE packages.