My exam strategy went thus, I read the HFS book twice, and the Servlet spec twice. In the HFS mock exam at the end, i got 86%(I didn't have any coffee that day). The exam was tougher than i expected. I had to mark around 10-12 questions and went back to them later. But the exam itself lasted 75 min. From the exam questions, I felt that the EL and JSTL parts were tough and HFS was not sufficient. Except for that, thanks to Bryan, Kathy n Bert for a great book.
HFS is "Head First Servlets and JSP". I take it that you mean Hanumanth Deshmukh's book when you say "Exam Study Kit". If you are going for the new SCWCD for j2ee 1.4 platform, then HFS is better. But if are taking the older version of the exam for the j2ee 1.3 platform, you can stick to the study kit.