I agree with Roger that forcing a depth vs. breadth choice
might not be the way to ask the question, but I'll comment
anyway.
Most of the courses refered to as depth courses focus not
only on the physics content, but on developing a way to
think about physics (critical thinking, if you want a
buzzword), a way to ask the right questions, a way to
think up good experiments to answer those questions. This
includes, but is much broader than, problem solving.
Students (especially, but not only, inservice teachers who
take these courses) often comment that the way they think
about the world has changed. Once these skills are
developed, it is much easier to pick up breadth, either in
another course or on your own. I don't think it works so
easily the other way around. It is much harder to get
depth, with only a breadth background.
It is not that the students will retain all of the depth
they have learned the first time around, but they tend to
retain some of the thought process, which is a useful skill
for further learning.