What's the sonic advantage of bi-wiring

In every situation where I've biwired, the sound quality improved. This was limited to using the same quality cables in both single wire and biwiring. I have never compared more expensive single wiring to lower priced biwiring. The typical benefit was an increase in midrange clarity.....similar to the difference when using good power conditioning.....the offending artifacts aren't that noticable until removed.

I think I first experimented with biwiring with Mission speakers in the mid 1980's.

Cable makers in general are not surprisingly behind bi-wiring...intersting to note that Wilson, a premium maker, doesnt see the benefits...which mirrors my experience...to each his own...

Asked another way, is there a disadvantage to bi-wireing speakers having the required binding posts.

I biwire my Apogees, but that's no surprise because they pretty much HAVE to be biwired due to their low impedance. It's very noticeable, but maybe not so much on other speakers that present less of a load to the amp.

That being said, I use the same wire on both tweeter and woofer. I do see some biwire cable companies using different wire for tweeter and woofer (or perhaps just different gauge). I would think you would want to retain the character of the wire on both top and bottom, so using the same wire for both makes sense to me. But I can understand others thinking "more transparent on top" or "more tingly" and using silver on the tweeter with big gauge copper on the bass.

What do you use?

Are you sure those dual/jumpered posts aren't there mainly for bi-amping, bi-wiring merely an incidental afterthought? Bi-wiring is a relatively recent practice. Bi-amping is not. Adequate guage is what matters. Where are the dual posts when you choose to bi-amp?