it's not exactly true that the more wood, the less chance of warping. that can be very hard to say really. Think physics. if 2 pieces of wood warp away from each other, both give a reaction force on each other. That's the best analogy I can think of.
In theory 3 piece necks should be cheaper than a since piece. But rarely do you see a difference.
The general consensous is simply that 3 piece necks tend to warp less than a 1 piece neck. It would be extremely difficult to deduce anything more.
Like ShredCows put it, need a good tech/luthier to explain in detail.