I managed to find someone in st. Louis with an Olwell nicholson.
My wife and I went to see him this afternoon and
I played it for a good while. Brought the Olwell Pratten too.
The flutes are quite close. The nicholson has slightly
smaller holes and a very slightly shorter span between
them. It’s a little more comfortable
to hold. But, for me anyway, there’s no major
advantage in comfort.
The Pratten has a bigger and more dramatic sound.
The Nicholson has good volume and is more a bit more
focused. Of the two we preferred the Pratten,
though both are good. Go for the gusto!
My impression, then, is that if one is already happy with
the Pratten, the Nicholson doesn’t do anything
different enough to make it terribly desirable,
though it is certainly a lovely flute.
FWIW, YMMV, subjective as all hell, and so on.