Loads, levels, scenes

I’m pricing out a job for a client who knows enough about Flash to be dangerous. I’m trying to convince him about the virtues of loading separate swf’s into empty clips and/or levels. His dabblings convince him Scenes are the way to go because everything is in one file, no worry about a clutter of files.
So maybe you (gentle readers) can help me come up with reasons for how loading externals is better. Here’s what I have so far:

  1. File size. No huge file to load in at beginning. Files load as needed, IF needed.
  2. _root. With multiple nav buttons and “chapters” senes make it harder to keep track of _parents and _root.
    What else can I say?