1. What's the difference between low D and high D whistle? What are their ranges ? Is high D whistle is another name for soprano whistle?

This link suggests to buy a D whistle - no mention of low or high.
http://www.wikihow.com/Play-the-Tin-Whistle

It mentions the range of the D whistle

The standard range of the whistle is two octaves. For a D whistle, this includes notes from the second D above middle C to the fourth D above middle C.

But this link suggest to buy a Soprano D whistle as the holes are closer, so a beginner will be able to get a grip of the holes easily. The holes in low D key whistle are further compared to high D whistle and will be hard for beginners to learn.
http://www.thewhistleshop.com/beginners/lowd/lowd.htm

But they didn't provide any range chart for either Soprano D or low D. So,

how do I know what are the ranges of Soprano D or low D before buying one? Is the starting D tone in low D above middle C or below middle C? Is Soprano D whistle just another name for high D whistle?