As an inspector, I think we have done our due diligence if we just follow the tables in the back of the NEC. As in installer you have to understand if you up size the raceway or the box over the minimum, your job is easier. It will not be as hard to pull in the conductors and easier to put the box together. It is like wire bending space. I can tell someone what the minimum size is but I still do not actually have to bend that conductor to make that turn.
