Marie asks: Which is easier to take, the New Construction or the Commercial Interior Exam?
The answer is totally subjective to the person taking the exam. If we had to choose (don't hold us to this) its our GUESS that the NC exam is more difficult than the CI exam. The NC exam study guide is over 400 pages long and, broadly speaking, the scope of a new construction (ground up) project is typically much more complex than an interior retrofit or design.
One could speculate that while the paperwork levels required for both LEED types may be comparable, the margin for error on an NC project would be slimmer than on a CI project. There's no easy answer to your question.
Hopefully someone's out there who's taken both exams who can testify as to their opinion on this subject!