Very true. I guess I was more thinking about the calcium content most of all... say if you were keeping a softies only tank, then calcium would not be of that big of importance when picking the brands (unless you are also trying to keep a healthy coraline going).
For me, with a 24g tank, the salt was not that big of deal. As my 5 gallon weekly (well, almost weekly ) water changes replenish a lot of elements compared to water changes done on a much larger tank.