I've never paid for a listing in the Yahoo directory and I have multiple sites that show up in the top 3 on their search engine. That doesn't mean I don't want my site to be listed in Yahoo's directory though. Yahoo has been around for a while and their authority on the Internet is off the charts. It's like getting a link to your site from DMOZ, minus waiting the months, if not years, it takes to get your site approved for the directory. I'd go for the Yahoo directory link if you're considering it.