Well in most cases development is better. This is a question that is continually thrown around here at Namepros so I'll try to give you points from both sides and then my own input about it.
When you develop a domain you open it up to visitors, getting listings in search engines, and the potential for revenue. All of these factors drive up the value of the domain. However, development does take time and a certain amount of skill. You want a website that fits the topic, looks decent or better, and properly optimized for ads. Not to mention the time needed to let these factors take effect. However, value potentially increases exponentially with proper development.
On the other end just selling the domain is "easier." You're not involved in the time and effort it takes to create a website so the overall process usually is quicker. This is assuming the name will sell though.
In the end I always say development is better but use discretion about what you develop. You don't have to go one way or the other with every name you come across.