Lap times. The point is to go faster. You can set timing based off amp draw, and compare numbers on dynos, but ultimately the point of adjusting anything is to go faster. I run esc's with data logging capabilities so I can see the numbers as the car is doing what it does, instead of how an analyzer is just running a motor unloaded. I make all my adjustments and check them on track to see how the lap times are impacted. I start with motor timing how it is set out of the box, and gearing I know is safe. Run the car, make a change and run it again. Usually if a motor stabilizes at about 150°F after a full battery, the motor is running in the sweet spot. This is my method for my 17.5 2wd buggy, but the method works for any spec motor class.