The modification kit does improve the ventilation on a Langstroth. What the modification kit doesn't give you that the DE hive has is less propolizing and brace comb.
I find the DE mod kit top cover a little cumbersome, So I use the vent box with a normal telescopic cover.
By the way, David does not agree with the claimed benefits of SBB. I believe his point is that the warmer/humid conditions of a brood nest without a SBB is less ideal conditions for varroa.
I do use both, but as Brian stated, it can be too much ventilation, so I only open the SBB June-August.