Any question answered...

Bushed chains have the definite advantage that they spread the load from the pins and the rollers over a larger area than 'bushingless' chains which have split bushings formed from pressing protrusions out of the inner plates.

They have the debatable advantage that the only way to get to the pin-bushing wear point is by squeezing between the inner and outer plates. This makes it much harder for contamination to get in, and much harder to flush it out when it has. (Sheldon has an article arguing that split bushings are better, but also hosts a Jobst Brandt article decrying split bushings...)

They have the conditional advantage that the bushing creates a rigid link between pairs of inner plates, making them less flexible sideways. This is good if you don't have dérailleur gears and your chainline is straight.

Nice info. So are most track chains bushingless these days, despite the advantages you outlined? My kmc 710 is bushingless