On Slashdot, you get stories of general interest without "What's this doing on HN?" or "I wonder if a startup could disrupt <whatever>?" bullshit comments cropping up. People can post humor for the sake of humor without getting stick-up-the-ass shitheels posting high-and-mighty "we are not amused" replies and downvoting. Slashdot feels fun and maybe a bit incendiary. Hacker News has great content and a lot of great posters, but it also has this atmosphere of constantly trying to make yourself look as smart and perfect as possible, taking yourself way too seriously, and most importantly selling yourself/your startup at any opportunity.