I have one of their nickel whistles in C and its not great, but then its a cheap whistle. I’ve noticed a lot of people love the Bb whistle in general, and today I watched a nice video of a brass Generation Bb being played and it sounded great (I will no doubt be getting one at some time…) The player told me that their C whistles are bad, but their F and Bb are great. Which seems strange seeing as they come from the same factory (I assume)
But also what is it about Bb whistles in general that so many love? Its only 2 semitones lower than a C and 2.5 lower than a D. I suppose its because the pipe is longer, and wider (?) giving a warmer tone?
I love Generations in general.
Yes each size has its unique sound, not better or worse, just unique.
The thing about Generations is that they’ve varied quite a bit over the years, and within each time-period there can be quite a bit of variation from whistle to whistle of the same size. Even whistles made in the same batch or run will vary from whistle to whistle.
This means that IMHO it’s meaningless to say “C Generations play like _______” or “Bb Generations play like ________”.
For example, I bought a C Generation back around 1980 that I still play. I’ve yet to play a C by any maker at any price that I like as much.
However though I’ve tried a huge number of Bb Generations over the last 45 years I’ve never come across one for sale that I liked. (I have a drawer full of mediocre ones.)
This was finally solved when I got a Jerry Freeman Generation Bb that plays exactly how I like whistles to play, just like my trusty Generation C.
When I first started out with whistles, I bought 2 complete sets of Generation whistles, brass & nickel, they all sound good & play easily.
I’m guessing that I bought mine when they were at their best. 
The Bb & A whistles are favoured because of their tone & easy playability for most people, whilst the low G & low F are bought because they have that mellow low tone, without being too big. 
If only Generation, or Feadôg for that matter, would extend their range. Generation only go to Bb. Still better than many, who only tend to offer D or C.
I’d love to try a mid-low whistle, something like a G or F. I had a low D but I couldn’t get away with it even with the Piper’s hold
That’s where Jerry Freeman steps in. He takes Generation Bb heads (with his modifications) and makes new bigger bodies to go down to A, G, and even lower.
I have a self-made Generation A and a Freeman Generation G and I love them both.
Does he still make em? And are they available in the UK?
One stockist, unfortunately all out of stock presently - https://bigwhistle.co.uk/freeman-tweaked-whistles/
(Personally, at those prices, I’d be looking at Dixon or Shearwater.)
Yea that does seem steep.
Bb is four semitones lower than D.
Here’s one player who made good use of the Bb Generations:
Kieran Collins - Maude Miller/Dunmore Lasses
That would be the first one that would come to my mind anyway.
Other occasional users have been spotted though 
:
Thought that was Mary Bergin at first
It is, isn’t it?
The photo is showing her playing a Bb, I think she used an Eb more regularly though, (just what I’m remembering reading here).
Kieren Collins video is showing a Bb being played.