When comparing Eye of Gnome (eog) vs nomacs, the Slant community recommends nomacs for most people. In the question“What are the best FOSS image viewers for Linux?” nomacs is ranked 1st while Eye of Gnome (eog) is ranked 3rd.
Question Ranking
Pros
Pro More lightweight than other kde or gnome dependent applications like gwenview, gthumb or kphotoalbum
Pro Double-click to view Fullscreen
By default, double-clicking on the current image opens it in Fullscreen mode. This can be turned off in Preferences if desired
Pro Image Slideshow
You can view a slideshow of all images in the current folder, and adjust the delay between images in the Preferences dialog
Pro ESC key exits Fullscreen and program
Pressing the ESC key exits Fullscreen mode, as well as exits the program ... hence press the ESC key twice and you're out
Pro Can set image as wallpaper
You can set the current image as your desktop wallpaper directly from within this program
Pro Detailed view of image metadata
Pro You can work with hot keys that can be reassigned as you want them
Pro Frameless view
Pro Allows to cut (frame) images
It is important if you have to work with photos of documents and want to cut off the background on which you made photos.
Pro Highly customizable
Pro Lots of Image Adjustment Tools
Pro Comparing two images
This feature is called Synchronization. With the synchronization it is possible that multiple viewers perform the same action (like panning, zooming, etc.). This feature is useful when comparing two images. More at http://nomacs.org/synchronization/
Cons
Con Still have gnome dependencies
Con Returns to default settings after update
which is unacceptabe!
Con Recent version has slowed down
The latest version (3.8) suddenly became very slow in Fedora 26. Slow to step from image to image; slow to open a directory; slow slow slow. Downgrading to the previous version (3.6) restored speed.