The aforementioned BRS video is informative. The big takeaway is that after a battery of tests and comparisons, it was determined that the salt brand you choose is not going to make or break your reef. All of them will sustain a healthy reef. There are some differences in mixing time, water cloudiness, levels of alkalinity, Ca, and Magnesium, etc.
I've used Instant Ocean since 1986 and see no compelling reason to switch.