Premium directories market themselves as being the best of the best. They do not cut any corners and offer top quality options when it comes to everything from link placement to keywords, category descriptions and site design. Of course there is usually a catch to this situation and in most cases it is the payment price. Premium directories often charge a higher than market value price to allow website owners to add their URL and other website details. In the end it comes down to your advertising budget, if you can afford the extra cost then in theory you should be getting a better product and higher search engine rankings over time.