Maybe, some performance comparison or some noticeable specific differences is what I want to know.
As I heard there is no really big difference. Hence, I've got one more question. For what purposes dozens of people spent their time to reinvent the wheel implement already implemented spec ones more?
JSF was not, initially, open source. (eWeek in 2005: Sun Open-Sources JavaServer Faces) This prompted a couple of clean-room implementations to start so the spec could be used and distributed more freely. The terms of the Mojarra CDDL+GPL license aren't going to suit everybody, so there is still incentive to continue development under the Apache license.