I have used both. For the Ikelite strobes, I used the hardwired connection. It has a disadvantage of introducing one more piercing of the housing. It never failed in hundreds of dives. It was frustrating getting the strobes connected right initially. You have to align the pins just so. The strobes are wider, more powerful, faster cycling and hold a charge a long, long time. It has plenty of charge for a day of diving. And the clamp on seal for the strobes is good but if it fails the strobe is toast. The strobes are heavy and large and unwieldly. So, moving them and adjusting their power was difficult and getting them in a tight situation was a pain in the …… and usually unsuccessful.
The Sea and Sea YS DS are nice strobes. I connect them via fiber optic and that works fine. The strobes use rechargeable AA batteries (4). The strobes give decent power and are enough (they say) for 200 shots at full power. I do not use full power that often so I can probably get more. I take about 70 shots per dive so 200 shots does 3 dives. Also my mirrorless camera is good for 200 shots (or so it says) but it depends on how you use it. For wildlife photography, a battery will get 900 shots for me (camera not strobe).
The pluses of the Sea and Sea are - if it floods the batteries are toast. But usually with cleaning and drying the strobe will work. The battery compartment is separate from the strobe. If the strobe does not work after flooding, I understand sending it in will get it going again. I have not done this yet. The strobe can be a bit tricky to seal correctly. You have to put it on a hard surface and press down on the battery lid evenly and hard (or that is what works for me).
The advantages of the strobe is it is a bit narrower in beam and for me that gives less backscatter. Also it is far lighter and more compact making it easier to adjust the strobe placement, get it into tight spots and to adjust the power level. I shoot macro and wide. For macro, moving the strobes is really nice.
That being said, both strobes are fine performers. They both have different strengths and it is a matter of deciding which you like better.
If you can, I would try to go to a shop that has these and see how they fit with your rig. Some shops will let you try them out in the water for a fee.
