Yiistrap Vs Yiiwheels

What is the difference between them? Pros and cons? In getyiistrap.com Chris states: 2amigOS! also maintain their own extension library called YiiWheels that includes many more widgets. yiiwheels.2amigos.us/ says yiiwheels is an extended library of yiistrap. Looks like better go for yiiwheels. Any thoughts? Thanks.