Bi-wiring makes no difference, The back EMF isolation theory is complete nonsense because the crossover already keeps those currents away from the MF and HF drivers. The larger gauge wire claim makes no sense either, because the second pair of wires isn't connected to the woofer except maybe by a common ground if in the unlikely case the crossover was wired that way.
Bi-Amping is a different story. Properly done with a low-level crossover before the amps and bypassing the woofer passive crossover elements, eliminating the series resistance (and consequent loss of woofer damping) and hysteresis (delay between input and output) inherent in a series inductor will make a very noticeable improvement, as well as increasing the systems dynamic range by as much as 6dB.
This is basic electro-physics 101.