HN serves a rather specific goal, it is basically PG/YC's playground. This community will never be allowed to deviate much from their interests. That's a given you know pretty much when you sign up though.

At the very least Reddit is far more broad. So of course you're going to find a subreddit where you feel you belong. Some just might have to search further. In a way that's an easy statement to make though akin to "If you date enough people, you'll eventually find your soulmate."

Anyway, the comparison is moot due to the size difference. Its more fair to compare subreddits or groups of subreddits (how does that work?) with HN. Such as say startup-related subreddits.