8AWG silicone wire
This kind of EXTREME silicone wire is made by professional R/C manufacture. The conductors inside are 5-10 times more than regular wires. For example, the 10 AWG wire has an unbelieveable 1946 conductors inside.
Why call them EXTREME wires? Because the copper conductors inside the wire is smaller than most silicone wires even those designed for R/C application. The diameter of the conductors inside is 0.06mm (compared to 0.08mm regular R/C silicone wires).
Why conductors smaller is better? Because the same AWG (the same cross section area) wires have the same Direct Current (DC) Resistance, but the smaller conductor wire will have smaller Alternative Current (AC) Resistance because of Skin Effect.
But my battery is a DC source, why I need to consider AC Resistance? Because your Brushless motor is not a DC load at all. You Brushless speed controller is actually a 3-Phase inverter, it converts DC to 3-Phase AC.
Even if you use brushed motors, the voltage is not pure DC, because you controller is a Pulse Width Modulation (PWM) controller, your DC voltage is pulsating.
Another benefit of smaller conductor is better flexibility.