All else being equal, I wonder about the harsh(er) ride of deep wheels vs decreasing pressure to get a more forgiving ride and where the line should be drawn.
I do know that rolling resistance of the Vittoria Rubino G+ Speed tires which I use increase significantly below 85 PSI according to the rolling resistance site. For me, that's the practical limit and I won't really go lower even if it means living with the harsh(er) ride of deep rims compared to shallow alloy wheels.
Whether that harshness decreases speed on rough pavements is not something I'm convinced of.
-Tim-