Take a look at the graphs and it'll show you the difference. Depth has the flattest response.
Flattest response in that room. Not the same thing, but might be a good indicator. Best would be to take measurements in your own room. Room plays a huge role.
From what I remember flat is supposed to be the flattest, depth was to add a bit at the lower end, punch a bit more in the mid bass range...
^^ What he said..
In my room there is hardly a difference between "Flat", "depth" and "Punch"... the only difference from my measurements was that punch boosted around 60hz by 3-4 DB