JSF gives you lot of predefined, rich controls that offer functionality would have to implement manually otherwise. The price for it is giving up control to certain degree in how user interact with the application and about HTML generated. It can also stand in the way of integration with JS libraries.
Debugging and testing is considerably simpler with JSP and specially with Spring.
It really depends on feature set of your web site, skills in the implementation team (and support team), time to deliver constraints, etc.
I personally prefer simpler technologies that give more control to the developer (JSP with Spring MVC) just for the internal elegance of the framework but that is never deciding factor ....
