You've come immediately to the matter in question.
I've always preferred a larger grip for serving and coming forward.
Occasionally I'll hit a semi but never a full western FH.
For me the larger grip works well.
For those that hit the semi or full western, I would think a smaller grip is essential to getting the necessary racquet head speed. This however, may affect the serve.
The reason for asking is that my 'protege' is finally make the leap from the PS Original 85 to a Head Radical Microgel. He plays an aggressive game from the baseline and does not hesitate to move towards the net on weak shots. He also plays both singles and doubles, so there is a fair amount of net play to consider. Previously, he has built up the grips to approx. 4 3/4+ allowing ample room to slide your index of the off hand between the tips and heel of the racquet hand. I've recommended that he try the new stick with a smaller grip for a few weeks to see if it helps his FH and/or affects his serve and net game.