IO for me. I've used it for 4 years with no problems. I find the Ca to be a little low about 360 when mixed to 35ppt, but a sprinkle of Seachem's Reef Advantage Calcium and I'm good to go. I get a nice 4.0meq/l for alk so, no issues there. IO has gotten better over the years when it come to mixing clear. Yes, 4 years ago it took a lot longer to clear, but now 30 minutes and clear as a bell.
I can buy a lot of RA calcium for the difference in price between IO and Tropic Marin PR.