If you can discern a difference between a 6 foot and 12 foot power cord you are God's gift to humanity .
Although I think a case can be made for good shielding a power cord to reduce electronic interference along its journey from the outlet .
Also I would opt for 10 gauge all the time just to make sure there's plenty of pipe room in those moments where Power demand needed but no one is able to really know for sure.
Also as you may have guessed in this hobby you feel better when you spend more money otherwise you'll always wonder should I've spent more money on something maybe it would've sounded better and by spending more money you eliminate that thought. That's a really important consideration.
If everything else fails and you're still unhappy you can buy a puppy and if you get bitten there are those that believe it's OK to shoot it.