i dunno how to put it... i have similar proportions to you and my wrist size is circa 6.5"-6.75".
i have watches both from 36mm to 42mm size, and i think they all work well, whichever i decided to pick up for that event.
but personally i would not wear anything bigger than 42mm for a dressy event. i dont want people i talk to, get distracted by the watch.