Significant how? Have you worked out the difference in voltage drop that upgrade buys you?
A $15 14 gauge cord has 61% less resistance than an 18 gauge wire. The $199 über-cord has 78% less resistance than 18 gauge. Over 6' drawing 10 amps, a 14 gauge cord will drop 0.36 volts, and 18 gauge cord will give up 0.9 volts. Given the information from über-cord's site, their cord is equivalent to 12 gauge, so the loss over 6' will be 0.24 volts. Nice 0.036 volts/$ improvement for the $15 cord over the stock 18 gauge; less so 0.003 volts/$ improvement with the über-cord. Better yet, plug in 6' closer to the electric panel.
Does any of this make a difference one can hear? We can all try this at home by A/B testing with and without a 6' extension cord. Or to exaggerate the effect, try a 25' or 50' cord.
The über-cord is handsome, but I think I'll pass.