This winter I visited the new natural foods store in Lawrence and found Super-Natural grass-fed dairy cream. Katherine and I put it to the test by making butter (on right) and comparing it to butter made from standard store cream (circle on left) and a pat of store butter (square). For color and flavor, the grass-fed cream made a far better product. The yellow color corresponds to the amount of beta carotene (vitamin A).
In late February, after my first calf arrived, I milked out a half-gallon of our own Bluestem milk to see how it compared to the store-bought grass-fed cream. The Super-Natural cream made the butter on the right, and the small bowl on the left contains Bluestem butter. Ours was a little more yellow-orange than pasteurized cream, but the difference was not nearly so stark as between the grass-fed and standard store cream butters.
So, if you don't have a cow of your own, I'd suggest the grass-fed cream/milk/butter. It may just be worth the money!