The best thing about using WPA over WEP is this greater level of protection is not only using it for networks setup for home computer use, but more importantly for the expanding use of Wi-Fi hotspots for public use. Using WPA ensures a least the minimum compliance to wireless security is met.
Thus WPA is considered to be an improvement on WEP because it has a centralized server to authenticate the connection, and it also relies on Extensible Authentication Protocols (EAP). However, a lot of Wi-Fi points still use a mix of WEP and WPA to support people who are using WEP. As a result, there is less security for the users who are in mixed WEP/WPA mode as WEP security over-rides. Instead WPA is preferred for home use that is not in mixed mode, because it provides a greater level of protection.