Well, it's obvious that, a very large percentage of HN users are reddit users. I prefer HN for the better, startup and technical oriented commentary and community. I think reddit devolves too fast as the discussion length grows (plus I like HN's simple layout better).

Right now I check reddit before I check HN, but mainly for topics other than those covered by HN. It's disheartening to see cross posts reddit->HN though, since the communities are virtually the same. But I'll admit that the same topic will get better discussion here.