For my ears - a bit like Nigel’s post if I have understood it - I prefer the sound of lower whistles because to my ears they fit more with voices.

Playing tunes is different. And often n a session having a high instrument singing out somewhere in the mix of things is just beautiful.

A lot of songs have a range of an octave to an octave and a third. Some songs an octave and a half but much more rarely. I think all the songs I posted are under an octave and a half. I haven’t checked!

And instruments have a much greater range than most human voices that you would enjoy listening to in a folk context.

So my understanding is that you try and pick a whistle that can not only play the notes but play them in a range that fits with the voices and the range of the notes in the song? If that makes sense? I may not be explaining what I mean well