Mark,
I will make one assumption: you are comparing the Sea & Sea YS-60 TTL/S to the Ikelite 50s.
There are some differences, but both strobes are excellent, in my opinion. I am testing my memory a little here, but as I remember from my strobe-buying days the YS-60 is a little more powerful--i.e., has somewhat large GN.
However, the Ikelite cycles faster--i.e., is ready to take the next picture sooner...about 1/2 second as I remember.
They both fire about the same number of flashes per set of batteries.
Some photographers and salesmen in photo shops think the Ikelite is a little more awkward to use. I cannot comment on that.
The YS-60 has a little larger coverage angle and,so, will be better for wide angle.
But I want to stress that both strobes have excellent reputations among the photographers that I have met.
You did not mention the difference in price, but I suggest that you try more than one source. For Sea & Sea products, I have found that Berger Bros are great. Their URL is
http://www.bergerbrothers.com . They also carry Ikelite.
I hope this helps.
Joewr..feeling a little rushed.............