It seems that salts are solely based on opinions and individual targets. But, I started with, and have been using, NeoMarine for about 6 months now. My reef loves it, so I love it. From the water I tested in the Caribbean, this salt matched the best, IMO.
In the Caribbean, I found...
Temp at 83 degrees
Salinity at 34 ppt
Calcium around 405-410 ppm
pH at 8.2
Alk at 7.5 dKH
Mg at 1283 ppm
Reef Crystals boast a calcium level of 450 ppm. That is good for some individuals, but I want my water to be as close to natural as possible.
Again, salts are a preference and are based on opinions and individual targets.
These are my findings and my preferences. My advice is to find a salt that meets your preferences and targets, and be consistent with that salt.