For many years I've gone along with the idea that Prattenesque flutes are 'tune cannons,' good for loud sessions but less expressive and nuanced than Rudally flutes. I am wondering about this, especially in terms of the Olwell Pratten, which I find as expressive as any Rudall I've played. The Pratten has a more open sound, the Rudally flutes are more focused, but I don't see why this, in the hands of a good player, would make a difference in expressiveness. Opinions?

As far as I know it is flute players rather than flutes that are expressive! I have both and they both can be played sweetly or harshly.

Yes.

Specificially in the realm of slow airs I would say more so than a Rudall. The Olwell Pratten, for example, and I would wager a Hammy, just have that inexplicable depth that I have not heard elsewhere.

Thanks, everyone. Another stereotype bites the dust.

Oh, no! Don't call it quits just yet. I was watching and waiting with great interest.

I have an Olwell Pratten and it's a very good flute, but I prefer to play a Rudall Carte that I have, or a Wilkes Rudall model. For me they have a better sound, more nuances, more interesting. But that's just me, I suspect a lot depends on the person playing the instrument.

I can only speak from my limited experience from making flutes and whistles (maybe around 50 instruments all in all) -- on a flute with bigger holes the stopper can be set further out. And that extra bit of air above the embouchure hole makes the flute more "elastic" for lack of a better word. You have more leeway or more headroom. So it can be played a bit more expressively. But I am not sure if the stopper is set at a different position when comparing pratten and rudall style flutes because I don't know if the bore will be the same. And there are so many other factors -- the biggest (apart from the player him/herself) being the embouchure hole.
But in general, all other things being equal, bigger holes and a stopper set further from the embouchure can make the flute more expressive. But it can also make it harder to play as it takes more air (depending on how effective the embouchure cut is -- my guess is that an Olwell will still take little air) and it's easier to blow it out of tune, which on the other hand means, vibrato be means of variating air-pressure (not finger vibrato) will be more effective.
Just my two cents. I guess the reputed makers here on the site will have tons of more info and details about why one style of flute plays differently than another.