OCF: Sync speed - PC Cord vs. TTL off-shoe cord

I've recently started experimenting with off-camera flash - I'm using a 580EX and 430EX. The 580 is in manual mode off-camera, triggered by PC sync cord and acting as wireless TTL master to the slaved 430EX.

The trouble I'm having is the slower sync speed for the wireless TTL slave. When using a PC cord (with a hotshoe adapter) the 580EX will still sync at 1/250s, but the latency in getting the slave to fire forces me to shoot at 1/160s or slower. (This limitation has been discussed in previous threads in this section.)

However, using canon's off-camera shoe cord, both Master and Slave sync perfectly - right up to 1/250s. My question is, why?

Would a longer E-TTL off-shoe cord (à la Flashzebra or DIY variety) allow both flashes to sync at 1/250s as reliably as an original Canon cord?

What is the maximum working length for an E-TTL cord, assuming we use a 580EX on the other end?

Thanks for your help and replies.

A pc-synch cable only transmits the "fire" command, which leaves the Master having to transmit a preflash with setup commands, etc followed by its fire command.

When a correctly-implemented off-camera TTL cord is used, the setup and exposure evaluation commands are sent to the master, and then the fire command. Both flashes are ready by then.

A longer cord such as FlashZebra's should show little latency, and may achieve 1/250th sync. Length will affect this performance.

Before long, we may see the release of a US$200 TTL radio trigger designed to replace the OC-cord.