What would a native Mac app do that a Web app doesn't, that would be so much better than the Web app?

I never figured that out for ADN either. I found a place in my life for a CLI app (wry for ADN), as a "I'm working but want to fire off a quick remark without getting distracted by reading" utility, but Nice obliterated any desire for a native app for me. And before that, I used Cauldron, which was only kinda-sorta-native.