This is the question I've always had about the Challenger, but never heard addressed: How much of a factor was the crew's opinion considered to be? I strongly suspect that the astronauts themselves exerted informal but real pressure to prefer flying, since it would be their moment in the sun.
I did work on astronaut EVA training, however. In that case, the astronauts were king. No matter how silly the request, their wishes were catered to - but only in areas of usability, not safety. It turns out it's really difficult to connect wires in space, for example - small things matter a lot. I can remember at least one case where what they wanted was just plain dumb. But we did it anyway. Usually, though, they were pretty good about that sort of stuff.