I have quick tip here, which is more management issue and less technical.
You will defiantly find some good  comparison on the net, with lots of pros and cons about each framework. This always happens! But now it is more important. JSF and Tapestry deal with two different way of looking at presentation layer. What I want to mention is the scope of the project and team experience. What is the team experience in presentation layer? Did they used to write Tag components and always think that they can make it common by a Tag? Did they used to develop with Struts? What is the scope of the project? Are they ready to switch to some thing new?

Here is a tip from one of my friends:
“We will switch to Tapestry from struts as soon as we start a new ‘small’ project. If Tapestry will become a JSF standard implementation, which seems very rare as it contributor mentioned that he does not want to change it anyway, we would switched to Tapestry today. ”