IO generally , but I've used everything on that list bar the seachem, plus some other you haven't listed, AquaMedic and Elos. I've had pretty good , similar results for all. If all things are equal I like IO for the consistency. I used to really like Kent, but there have been some batches recently with bad (effectively no) alkalinity, but generally it's what I can get a decent deal on.
There is apparently more Ca and alk in RC over IO, but hether it's usful is very arguable. Likely if you have a tank with few hard corals, and just want more coralline