While moving the push rod in or out on the bellcrank does obviously increase the total distance the push rod is going to travel, I think it is more important to think in terms of SPEED of the controls as Greg said. I personally use nearly all Windy's 4 inch bellcranks with the hole 8/10th of an inch from pivot. Bob Hunt uses 9/10th. that works for me too. I almost never use 3 inch BC's any more. But when I did Dixon told me to redrill sig BC's to 7/16. That worked for me. Those Old time control systems were toooooooo fast!
To describe it better, It's personal choice!