lol your electrical friend doesn't understand audio. Aside from the construction the 10 gauge lowers the impedance of the outlet. Your house-outlet-stereo are all in competition for power from the local transformer.
I am currently using 14 gauge pc. I use it for its construction but i also own 10 gauge pcs that brings its own benefit for current delivery.
It could be but the way he explained to me was, if I have a 1/2" pipe bringing water from my main water input all the way to my faucet, what benefits will using a 2' hose after the faucet? Smaller than the original 1/2" will restrict water flow and the flow will have more pressure but bigger will not provide any benefits.
Same for mains. If a 14AWG wire is bringing the current to all the way to my outlet, what benefits will be provided by using a thicker power cord (e.g. 10AWG) on audio gear.
I'm not arguing about quality of material/cable or craftsmanship (i.e. some power cords are built better than others), quality being equal or better, I'm questioning the whole cable thickness issue and wondering how much of it is marketing hype...