2S vs 3S is mainly about voltage and weight (assuming they are both the same mAh capacity).
Voltage makes the motor spin faster. So, you will be using a lower throttle setting.
Weight gives the crawler more traction.
If you are mainly about the "crawler" aspect, you may want to stick to the 3S and change the gear ratio (assuming there is an option for changing the gear ratio) for better throttle response for low speed.
If you can't change the gear ratio, you may get better low speed throttle response (and lower ESC temps) from the 2S.