(Alex, your grip sizing looks very similar to mine.)
I just find that with the smaller grip I have a lot more control and speed in manouvring the racket head and just feel that I am in total control of any movement in the racket, especially on serves and (surprisingly) on volleys. I can understand that hitting block returns is probably fine with a larger grip, but I just find that I can move my racket and re-direct the ball so much easier with the smaller grip.
All personal preferences though.
"Tennis is just chess with balls."
Using: Dunlop Biomimetic 300