I'd argue that "better designed" is subjective here. Hacker News is optimised for high content density. Designer News has lower content density, but there's more space between posts (and visual signposts in the form of "badges") which makes the front-page easier to scan. I appreciate both approaches.

While "better designed" is definitely subjective, I find that HN reads easier and is more visually appealing. Personally, HN feels superior on an aesthetic as well as functional level - many of DN's design techniques feel kind of cliched or tacky.