I've found that I switch between a few salts as to what on sale, but I only buy the same few salts: omega reef, red sea cps, and coralife salt.. Surprisingly coralife gave me lower mag cal alk but was cleaner as in less phos nitrate nitrite.. And the coral pro and omega reef were slightly dirtier phos nitrate nitrite but gives me higher mag alk cal..
I mostly use omega reef as the couple places I go to always have it in Stock and it's only 60$/180g .. It tests right around 11 all 470 cal and 1260-1300 mag every single. And it never leaves any films or anything.. When mixed dissolves in minutes to crystal clear water!