I just went through the same process about 2 months ago, choosing between the Inon Z220s and the Ike DS-125s. In the end, I decided on the DS-125s for a couple reasons.
1. I had personal experience with another Ike strobe, the DS-50, and was comfortable with the brand.
2. I could only buy a single set of strobes (2 of them) and felt that for very wide angle the DS-125s had slightly more power
3. I prefer Ikelite bulkheads to Nikonos ones, and there wasn't a sync cord available for Ike to Inon.
I definitely liked the Inon's, especially the size, weight, and the AA batteries. I just felt that the points above outweighed the benefits of the Inons.
Based on about 25 dives with the -125s, I've got to say, I'm very happy with them. They are definitely large and heavy is a factor, mostly out of the water. One thing I don't like is that they are hard to change settings on when you have them extended out at the end of 2 8" arms if you don't have the manual controller (which I don't). I find the 3 settings to be ok for the most part when shooting manual. More would be better, but I can't say that a lack of settings has seriously hampered my ability to get a shot. I'm the limiting factor, not the strobes.
Just to be clear, I'm not saying one is any better than the other, at least not in my hands, just that I chose the DS-125. If I was in the same situation as you (Seacam / MkII), I'd probably make the same decision again.
Hope this helps.
Tom