It generates screenshots with smaller file size and has an option to add delay before taking screenshots. I used it for a side project[1], but it would randomly die with segfault.
wkhtmltoimage generates screenshots as well. The filesize should depend on chosen resolution and image quality. Of course if you want something more sophisticated than jpeg you can always convert the output with a third party program.
With regards to delays, I think the --javascript-delay option does the same thing.
With regards to delays, I think the --javascript-delay option does the same thing.