I understand that floor clearances may be an issue in some road cars but I suspect there is a direct effect on the vehicles handling.
The particular example I am working on which has bought this question to my attention is a Westfield style Clubman being built by a freind for a street car. It is four link and uses a panhard bar. I don't know if is is equal or unequal length arms but they are all parallel when the car is viewed in plan.
He hasn't decided on anti squat / anti dive yet either but he is working with a horizontal lower arm at ride height.
I have had experience with one drag car guy who tells me 4° nose down is the go and another person who does street cars stuff who says 1° nose is all you need but neither can back up their claims with any reasoning. They jsut know this!