I have always been a fan of Red Sea and never had a negative experience with it. I went to reef crystals for cost but all it did was cause me to learn to choose quality or quantity.
I've always used IO and never had a problem, I run a calcium reactor and Zeomag to keep my parameters in check. I thought about trying the Red Sea Coral Pro, but the ALK is higher than I like.
I started out using reef crystals years ago. But for the last two years I have been using Red Sea coral pro and love it. Although this recent bucket I am using has been having a lot of calcium precipitation in the mixing container. Up until this point I have never had this problem with it.
I currently use plain instant ocean because it's the most affordable I've seen, but I have not been reefing long enough to comment on how well it works.