Slinkset lets you populate a social news site with submissions from a collection of RSS feeds. This is great for populating sites that are just starting out, and can also be used simply as an RSS aggregator. I don't think Reddit offers this functionality.
Exactly what I was wondering. And I was beginning to like slinkset too. Maybe I'll just keep using slinkset because it is the smaller of the two and for now, does everything I want.