Here is what seems to be the general consensus:
Advantages of Sync Cables:
1. They are not limited by the on-camera flash recycle time, and so are much better for rapid-fire situations (of course, you are still limited by the recycle time of the strobe itself)
2, Some housings now support electronic TTL exposure circuitry for auto TTL exposure, but these tend to be clunky, expensive and are not widely available for different housings or different cameras.
3. Work with any camera that has a hot shoe (ie, all of them).
Disadvantages of Sync Cables
1. As a general rule, no TTL exposure is possible, manual only (if you only do manual, then this is not a factor, but I love TTL for macro work especially)
3. Require additional seals, and can flood which can damage the cables and maybe the strobe.
4. Limited to the type of flash connector on the strobe and housing, so must be careful with compatibility
Advantages of Optical Cables
1. No housing or cable seals necessary, and no flood risk.
2. Less expensive
3. TTL exposure possible for virtually any camera that has a flash which can fit into a housing, assuming the external strobe has TTL compatibility.
4. Universally compatible
Disadvantages of Optical Cables
1. You are limited to the on-camera flash's recycle time. Some people try to get around this by going to manual mode and setting the camera flash at the lowest power, but it is still a lot slower than electronic cables. Some people try to use LED flash triggers which recycle instantly but you lose TTL and, again, these are not widely available across many cameras and housings. But, Nauticam does make these LED triggers for some housings and cameras, so check when you upgrade as you might be in luck.
I have an Olympus EM-5 (original) in a Nauticam housing. I use YS-D1 strobes with optical cables. I use TTL exposure almost exclusively for macro shooting and even for a lot of wide angle. I think the optical cables are great. The only area where they do not keep up is rapid-fire things like shark feeds or bait ball action. But this is a very tiny percentage of my shooting and I can adjust somewhat by going to manual exposure and setting the on camera flash to lowest power. This is still not nearly as fast as my friends who use electronic sync can shoot.
I also have the retras on order. I plan to use them with the optical sync, but I ordered them with the Sea and Sea electronic connection as they said that is the one most widely available, so I have an option. But, If I find I really need rapid-fire, I will probably try to find an LED trigger and avoid electronic sync cords and their potential for flooding,
Looking at your current system, you have the best of both worlds. Ikelite has really perfected electronic sync TTL exposure with a lot of different cameras, so you have TTL and rapid fire at the same time, if you want it. I would seriously consider staying with Ikelite for that reason. I think retra offered their strobe with an Ike connection.alone.
Edited by guyharrisonphoto, 27 October 2017 - 08:06 AM.