[Elgin Clock]

With our current setup and team inner workings, I don't think I can even choose one of those.

For us, we have the kids think up different ideas, and then both students and engineers work together to refine those into designs, and basically the engineers are there to help refine and make it work.
Entering our 8th year as a team in 2006, we have semi-standards for our robot that we know works, and we try and convey those as soon as possible to the students before build season starts in case we use those standards.
(ie: chassis and drive designs, and preffered 237 material selections)

Then the students do as much fabrication as their skill sets allow them too, and if something is too advanced, they either help up to a certain point and then watch and thus hopefully learn what the can't do, or help as much as they can to finish it for the most part.

So, basically the students as a (whole group) lay out a a rough draft, then the mechanical team (students and mentors) design the inner workings of that basic idea, and then the mechanical students work with our engineers to refine it like a huge engineering process... (Go figure!! lol)

I think that has worked very well for us in the mechanical aspect of the robot at least.

I can't really speak for electrical because A) I'm not that involved with electrical, and B) It's a whole different ballgame and not really based on designs and making it work, but brute force and dealing with the available resources and then making it work. lol