I am addicted to social bookmarking sites now and stopped using web directories. There are several reasons I think social bookmarking sites are better than free web directories.
social bookmarking sites approve your web site, pages, immediately.
you can submit any inner page to social bookmarking sites.
web directories take time to approve but no guanrantee.
I think my web site, new pages get indexed on search engines faster when I submit them to social bookmarking sites.
Thanks for reading and I hope I contribute something.
What you should also remember is that when using social bookmarking sites, people are actually going to look at them. That alone would bring more traffic.
Web directories are rarely looked at by anything other than search engines, so don’t really hold much weight in terms of traffic.
Actually I have noticed that even the SB sites that are nofollow are still ranking in SERPs. Try to search for certain kws and you will see. I have seen sample of the SB like Mister Wong (since we know that Mister Wong is a nofollow SB site).
Directory Submissions don’t work as great as it used to since webmasters are abusing it. Indeed social bookmarking sites tend to approve fast and they give better results not only in traffic but also in backlinks if you have good site content.