I'd say the main reason is curation; Hacker News has a lot of interesting content to be found in a single place. Okay, Reddit has some of that too, but it's spl

I'd say the main reason is curation; Hacker News has a lot of interesting content to be found in a single place. Okay, Reddit has some of that too, but it's split across hundreds of sections of which the vast majority of the content is just typical news or discussions. Feels like Hacker News provides a more rounded, more varied selection of things to read, and has more of a focus on said content being unique rather than it being new. Feels like a 'best of' list made up of submissions from 20 or 30 subreddits. I guess the quality of the discussion is better here as well, though I have to say it's generally pretty good on a lot of forums and subreddits, assuming they're not so popular to have been reduced to the level of the 'lowest common denominator'.