This is just my personal view, but I recommend using a double cord, for several reasons.
(1) At least with some strobes (e.g., Ikelite), the ready signal needs to be disabled on one cord or bulkhead port if you are using two single cords so that the camera only receives a "ready" signal from one strobe. The Ikelite double cord is manufactured with the "ready" line disabled on one cord, which is marked with a red band.
(2) Redundancy. Synch cords and the ports they plug into tend to be weak points in any system. Nikonos ports, for example, can be rendered inoperative if only a microscopic drop of water gets to the spring-loaded pins. If you have two functional bulkhead ports, using a double cord on one port means that you have the second port available as a back-up in case the primary port is damaged.
For what it's worth, I usually carry two double cords and two single cords for my Ikelite strobes. I normally use a double cord plugged into one port. If that port goes, I use the second port. If one double cord goes, I switch the second port. If that goes, I can still resort to the single cords, disabling the ready signal on one port. (One one long trip last year, I ended up with only one strobe and one single cord still working.)
I also carry a spare bulkhead port with a short ribbon connector that can replace one port on either of my housings. (Both digital and film housings are Subal, and use identical bulkhead ports.)
Robert Delfs