The answer to this questions, and to the "number of clicks" question, is
the 'it depends on the situation'. But the reason is the same.
For any interface where clarity or productivity are a primary goal
(there may be some gaming or community applications that do not belong
to this group), the way to achieve this goal is to enable the user to
understand and make choices without having to change his cognitive model
or derail his train of thought.
So, with these guidelines in mind, either test with real users or do a
heuristic evaluation of your design.
