LAX is my home airport.
Recently I've noticed that, during the times I fly, there is absolutely no one in the Pre-Check line waiting to have ID and BP checked, while there is a (minimal) delay waiting for an available CLEAR scanner and rep.
Since you can see the entire area just before you enter the CLEAR scanner area, you can make an instantaneous decision whether to use CLEAR or not.
This is in both T2 and T3.