The whole problem with C rating is that it's going to vary over the discharge plot of the battery, amongst other problems.

The 1/8 vehicles run higher cell counts, as was mentioned above, to get around the C ratings of batteries.

Higher voltage means better efficiency. This is due to IČR losses. (AmpsČ)*Resistance in Ohms gives you your wasted power as heat (Watts).

Wattage, being the good ole Volts*Amps=Watts, tells us 150 Amps at say, 4S Mid-Pack levels (3.9v * 4) is 15.6v, so ~2300 Watts of Power.

But wait, what's 2300 Watts at full pack voltage (4.2v)? 137 Amps.

And now at nearing the bottom third (3.4v)? 170 Amps.

If your IČR losses in the ESC and wiring are, say, 65w on that 4S pack, it means you've got running resistance around 0.0029 Ohms. Super low, but still 65w of power blasting off as heat, at 3.9v/cell. That dissipated power raises to a whopping 84w at 3.4v/cell, 29% more!

What's this got to do with C Rating? Higher C Rating batteries will hold up higher voltages as you put larger loads on them. Which means your whole system stays running cooler, longer. And this translates directly into equipment life.

This is why a lot of people push for 5S and 6S packs in the 1/8 Vehicles. Yes, it's faster, but if you dial down the top speed (RPM Limiter or the like), the whole setup runs much, much cooler. 150A at 3.9v/cell on 6S translates into 3510w of power, while pushing the same 65w of dissipated heat.

On the topic of ESC's, remember, a 120a ESC can burst into the 300's. Make sure you select batteries that match your burst, as well as your continual running.