The debate between absolute links and relative links continues to live on in the SEO world. The individual significance of each has been contested, but it is widely regarded that absolute links provide better SEO value on the whole than relative links.
Many believe that these type of links have less potential for getting messed up when search engines index your page. It shouldn’t really make a difference, but many conclude that this is reason enough.
Furthermore, content scrapers and RSS services may ‘repurpose’ your content legitimately (or not). In either case, shouldn’t a proper back-link be attributed to your site? This situation does not favours relative links. Although this is a minor argument, it’s still worth considering.