2S or 3S in my new Axial SCX10 III
 

Newly returning to a surface vehicle since my Team Associated RC10 days way back in the mid to late 80's. My SCX10 III Jeep RTR will be here in a day or 2. I have tons of 3S batteries here for my aircraft that should get me crawlin' right away but I intend to buy a couple new higher mAh hardcase Spektrum batteries just for the surface rig along with the new Spektrum 2100 dual charger. I'm using Spektrum gear in all my aircraft as well as the new SMART tech in my high end giant scale so I'm staying in that family.

What I don't yet understand is what are the benefits or pitfalls of 2S vs 3S in a crawler. This Firma ESC/Rx combo is compatible with both power sources. It's an obvious thing to me in an aircraft but does it relate similarly surface vehicles? Crawlers crawl.....is higher power output a bad thing in this case?

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.