When comparing Irfanview vs Lightshot, the Slant community recommends Lightshot for most people. In the question“What are the best screen capture tools for Windows?” Lightshot is ranked 5th while Irfanview is ranked 13th.
Specs
Ranked in these QuestionsQuestion Ranking
Pros

Pro Some editing tools included (cropping, color correcting, etc...)
Pro Lots of plugins available
Plugins can be found here.
Pro Batch processing
Even exif information can be batch processed.
Pro Recognizes virtually any image format
Pro You can just scroll with your mouse to explore images
Pro Ultra fast
If you press and hold the right-arrow button (for displaying the next image), you can watch images pass by as if they are a video, it's that fast. No stuttering, it loads images as fast as your hard drive can keep up.
Pro Lightweight
Pro Can use 8bf (Photoshop) filters
Pro Easy updates
Very easy to update the program and its associated plugins.
Pro Irfanview Thumbnail Viewer is a convenient way to view all image files easily
Irfanview Thumbnail Viewer is a great way to view thumbnails of all image files, including thumbnails of WMF files which Windows cannot natively display.
Pro Includes an image editor
Pro Clean interface
In spite of some drawbacks, the clean and easy to use interface is awesome.
Pro Available for macOS, Windows, or as a Chrome plugin
Pro Freezes the screen using print screen key
Cons
Con GIF viewing is buggy
GIF viewing has longstanding problems like flickering, incorrect framerate or artifacts, and it is very unlikely that it will be ever fixed.
Con Irfanview Thumbnail Viewer crashes on accessing AVI files
For some reason, the Irfanview Thumbnail Viewer crashes when it tries to access any .AVI movie file.
Con No transparency support
The alpha is converted to the selected background color upon opening a picture. When saving the picture again, you can select a color which is converted to alpha again.
Con Missing some utilities
Like browsing files utility.
Con Preferences are hard to find
Con Windows only
Con UI is far from ideal
Sometimes the interface is confusing.
Con No blur function
Some screen capture tools offer the option to blur parts of the image to hide sensitive info. It would be great if Lightshot did the same.
Con Cannot change the size of the text
There seems to be no way to make the text bigger or smaller when writing on the screen capture, which is a huge minus compared to MonoSnap.
Con No publicly available license
No publicly available license and inquiries to the developer were not responded to.
Con Cannot change the image hosting service
