Paid directories are much better than free directories. They offer high quality backlinks to your site, often including several deep links to your internal pages. Paid directories usually have honest owners who spend a lot of money promoting them, allowing your submission fee to be used for the good of the directory - therefore giving listed sites the best benefit possible. If your budget allows it, submission to paid directories is vital as it give a good boost your search engine rankings due to quality backlinks from authoritive sites.