Panorado has the most extensive grouping and most features of the viewers I tested.
LizardQ has a nice feature with EXR and HDR files which I was not able to test. If you have or can create an EXR or HDR file, then it would nice to test the tonemap feature.
When I tested LizardQ with a standard JPEG image, the Tonemap was greyed out. I believe it needs the file to be a .HDR or .EXR format.
The Tonemap adjustment could be the biggest feature advantage of LizardQ compared to the other viewers.
