You're going to get a lot of answers to this, I suspect. They might even all agree.
Between those two choices, I believe there is no question that you should use Subversion. Subversion was built as a "better CVS" and as a result, nobody actively maintains CVS any longer. Subversion has the ability to rename and move files without losing history, supports atomic commits, has a more robust repository format, has more modern access methods, has better third party tool support, and the list goes on.
