This will be a varied answer based on user preference, needs and availability.
I have used most every salt on the market especially having owned an LFS and received many sample boxes to try.
Instant Ocean is the most universal and used by most public aquariums such as georgia, shedds, Miami and New York.
My all time favorite was Salinity by Seachem but became hard to fin and when found was pricey
I also liked Aquaforest salt but for a time , it too was hard to find
I currently use Tropic Marin and it has done Very well for me.
In the past, I have used, corallife, Kent, Hawaiian marine and Reef crystal in addition to Red sea reg and pro plus Fritz blue. None I can say have let me down and its a matter of if you are focusing on fish, coral or both