RF3.3 is a great set of JSF components. With 4.0 it became even better and since newer versions are always going to be maintained longer than older versions, it's always better to choose a newer framework than the older one. Using JSF2 with RF4 is better than using JSF2 with RF3.3 (usually you would use JSF1.2 with RF3.3).
But for your Project it's important, to check, what your requirements are. Does RF3.3 or RF4 meet these? that should be the question you need to answer for your project.
Good luck with your project and best regards,