While Generation whistles generally sound very similar to Waltons and Feadog, We’ve heard the same complaint from many players.
It is considered the standard key, and luckily all of the whistle makers and brands offer so-called high D (soprano) whistles.
One of the most important things to keep in mind is that you definitely want a tin whistle in the key of D. They are usually inexpensive, with a price range of around $10-$20. You want to make sure they are easy to blow but preferably good enough not to provide the squeaks.
If you are a beginner and looking for your first tin whistle, you probably want one just to learn and start getting used to the instrument.