I'm assuming that by "having your own blog" you mean a link blog on which you submit links to stories you find interesting in your area of interest (as opposed to writing your own posts) and others can read it just like they read reddit or digg. In that case, I'd say that a social news site is better because it won't stop when you're on vacation or not feeling like posting. However, for a very small domain for which there is not a big enough community, a link blog is the next best thing.