What's the sonic advantage of bi-wiring

I prefer a single wire with jumpers to biwiring. I agree it really depends on the speaker and how the crossover is designed.

I have owned many, many, many speakers and outside of the Vandys, I always preferred the method above.

It's not always better. I don't know if it is my speakers, my amps, or the speaker/amp interface, but, my system sounds better not bi wired. It is better though using a double run of the same cables.

The cables may not make all that much difference - the speaker crossovers are probably the bigger determining factor for what if any benefit you might find with bi-wiring. There's some fairly good and accessible info at sites like Elliott Sound Products: http://lmgtfy.com/?q=elliott+sound+products+bi-wiring

I agree with the other comment above that this will depend on how the speaker was designed. Was the designer crafting the crossover with bi-wiring or bi-amping in mind? Or are those dual binding posts an afterthought, aimed at not losing potential sales t folks who may want to bi-wire or bi-amp.

Definitely biwire, no questions about it. The King will sound much better when biwired, as will the VAC amps.

I reviewed the King as well as the VAC Phi 200 amps for Dagogo.com. I bought the King following the review, as it is such a fantastic ESL, and without exception ran it biwired. You would be losing a lot of the speaker's potential if you did not do so.

The other option is to secure a very good quality jumper cable as opposed to the supplied jumpers. This will likely improve the sound nicely but I cannot say whether it will be as good as biwiring.

Now, the speaker cabling itself used for biwiring is critical; if a poor caliber of wire is used the system sound will suffer, but if you use a fine quality sounding wire your system will shine.