>>Thicker constructions, like five-ply or seven-ply, are overkill for most cooking tasks.
I'm not convinced that they're not actually worse. Heat conductivity goes down across each metal/metal boundary - and adding the weight of those stainless steel layers doesn't make sense.
IMO they'd really ought to be going on about the *thickness* of the inner (better heat conductor) metal.
Speaking of inner metal, the point of copper isn't so much that it conducts heat faster as it has less thermal mass, so when you drop the flame, the cooking surface cools down *fast*. No idea if that responsiveness translates with copper core...