A drop in pressure will in theory deliver a longer slower extraction, with a corresponding impact upon taste, making for a rich and lovely crema, with greater depth in the body of the espresso.
This is all good and well in a domestic setting, when youre not pulling too many shots per day
We dropped the pressure of my machine at work last winter, when trade dropped off a bit, and it produced wonderful results, not dissimilar to up-dosing.
When things started warming up and trade picked up, however, we got a very different result, as the machine was not able to keep up with demand, and kept choking the shots!
So we quickly changed it back again!
Based on personal experience Id be more inclined to go for bigger baskets, and greater dose, than less pressure.
Mind you, if I had the kind of machine that allowed me to easily experiment with both, I suppose Id reconsider somewhat.