I like tons of shelves, chins love to bounce around from shelf to shelf it is so fun to watch. I don't see why you would want a big empty cage. Fill it up! Lol. Even if that means you need to get another chinchi!
I think that it comes down to safety. I like just enough shelves that are properly spaced. This way the chin won't hurt itself trying to jump from one shelf to another that is too far away. I always set up my cages so that they have easy access to each level. I don't think the cage should be crowded, but they need plenty of spaces to jump and rest on.