Substitutes are never quite like the real thing.  They never quite look like the real thing, taste like the real thing, or feel like the real thing.  Artificial sweeteners may save you the calories but–face it–Diet Coke or Coke Light just doesn’t quite taste like “the real thing.”  The same thing goes for salt or butter substitutes.  You can’t quite compare what is churned from pure cream with what comes out of a laboratory in a plastic bottle with a picture of a cow on the label.