Why do potatoes grown in mineral-rich soils, such as those found in Prince Edwar Island, are better tasting than those grown hydroponically?

I don't know of any study that says taste is "better" on those soils. This notwithstanding whatever "taste" and "better" mean.

On the other hand, "The hydroponic potatoes are free from musty flavor and will probably be the best you have ever eaten."
http://askville.amazon.com/grow-potatoes-indoors-hydroponic-aeroponic-system/AnswerViewer.do?requestId=141653