I think the main thing I like is that it fits so seamlessly within my workflow. I can customize the functions I use to happen the way I want them to.

It has the same functions as the default app:

• ability to take screenshots of all or part of a screen (with/without timer)
• ability to take a screen recording of all or part of a screen (with/without a timer)

But it also provides options for:

• adding simple markup to your screenshot (lines/arrows/text/squares etc). As a developer, I often want to take a screenshot and add a bit of text or an arrow to highlight something to someone I'm trying to explain something to
• ability to do scrolling screen captures
• recording in MP4
• trimming screen recording videos
• removing or including audio in screen recording videos
• recording animated GIFs instead of video
• reducing resolution (for filesize) after capture
• hide desktop icons during screen capture
• change/hide desktop background wallpaper during capture
• options to customize shortcut keys for various operations, or customize workflow (for example I like screenshots to be automatically added to my clipboard after capture or markup so I can immediately paste in whatever chat I'm having with colleagues)
• options for keeping a history of screenshots/recordings
• options (I don't use) for cloud share/storage