I have fish only system.
For years, I spent a whole lot on Tropic Marin.
I then tried something different.
I went with whatever salt my supplier had on sale that week (large, large pet supplier located in South Florida and Long Island).
The only difference I ever noted was the way the salt dissolved.
The more expensive, the finer and the quicker it would dissolve in water.
Aside from that, I can't honestly tell you the fish ever complained about one over the other.
Don't know if corals will complain.