I let various factors dictate -- things that help maintain even canopy.
if something is more vigrous, i may cut it back slightly further for 2 new tops. I'll try to find a level where i can cut everything relatively to the same height. how many shoots do you need to fill space? figure 1 per 6 sq. inch. is good to go with excellent airflow. Fill space as needed with as many as needed. you want about 1/2 your intended bloom area... the stretch will take care of the rest. (assuming these are photoperiods.)
i'd also consider how many vertical shoots are sourced from "1" branch. I'd stil to 2-3 per axillary growth from apical meristem. Maybe 3 on the thicker ones and the former tops on apical meristem, as those will get more resources to share and vascular tissue to support it.