My 2¢-
I defoliated all of my plants to a degree my last grow and one in particular of all of it's fan leafs. In part to satisfy my curiosity of what the heck will happen and to increase air circulation inside and around the plant.
Some observations:
Trimming the emerging fan leaf on the leading tip reduces stretch. How much still seems strain dependent.
I had to harvest a wee bit early anyway, but fan leaf defo seems to delay trich maturity by around 7-10 days depending on the level of defo I imagine. At 69 days I was just barely getting amber where most others were already into drying
Bud size seems to be more dependent on available nutrition than number of fan leafs present. Fan leafs store food but their primary function is to shade the ground below to keep it from getting too dry. Because I pull cool air in from outside to cool my room, I think the extra light penetration helps keep my soil(roots) warm(er).
Fan leaf defoliation is really only necessary for better air circulation in cases where mold or mildew is an issue. It is for me until I completely seal my grow from outside influences.
Never trim branches or budsites after 12/12 unless absolutely necessary. e.g. salvaging a plant from bud rot or trying to prevent it during the last couple weeks of bloom.
My acquaintance over on G+ just finished a auto-flower DWC grow that he had to defoliate to keep from hitting the lights and then finally finish up at 102 days. Both of us are convinced there is a place for defoliation but it's not always necessary.