Why the smaller wire gauge?

[sanddrag]

Why is only 12 gauge specified for the 40A circuits? <R73> I would suggest everyone continue to use 10 gauge.

[jzampier]

I think FIRST likes to rely on the breaker tripping before your wire/insulation melts. I'm with you... I'm going to make my team use 10awg. (Plus 10awg fits into the terminals better...)
Oh, as a side note, its really handy to put a drop of solder on the terminals.

[greencactus3]

fat wire is good yes. remeber flexible with lots of strands is good too. and fat=heavier

[scottm87]

Weight. Wire weight can add up. FIRST is known for using wire gauges that are very low even though that size wire would never really be necessary. It is mostly for safety, and to eliminate the possibility of using too small of wire, but our team electrical mentor always complains/wonders why in the world FIRST chose the gauges they did.

In the end, the smaller gauge is just going to help in weight, and clean up the board a little bit if you have a large number of wires running.