70-620 or 70-624 for MCITP Enterprise
The final exam for MCITP Enterprise Administrator is an elective choice. This is the only elective MCTS choice that you get for the MCITP certification. Which one you should choose, really depends on your particular experience.
The two elective exams for MCITP are:
Exam 70-620: TS: Windows Vista, Configuring
Exam 70-624: TS: Deploying and Maintaining Windows Vista Client and 2007 Microsoft Office System Desktops