I'm wondering whether there are any real acoustic differences between these materials or whether it's mainly marketing hype.
Forgive the very slight delve into physics, but the thought I have in my head is that such differences as we experience are due to the amount the bell material 'wobbles' under pressure. And the amount of 'wobble' of sheet metal, all other things being equal, is broadly characterised by the quantity 'strength' (strictly Young's modulus) times the cube of the sheet thickness.
So if we have a standard yellow brass bell sheet of 0.5 mm and 'strength' 100 GPa (giving an Ext3 of 12.5) wouldn't it perform just the same as a beryllium copper bell (strength 180 GPa) of (the cube root of 12.5/180,000,000,000) = 0.41 mm or a pure gold bell (strength 74 GPa) of 5.5 mm? They should in (a very simplified) theory wobble the same amount for the same intensity of note. And that this wobble is much more sensitive to bell sheet thickness than material.
I suspect that the answer to this question is 'no', but for reasons discussed in another thread, I reserve my inalienable rights to ask a really dumb question now and then.
Btw. In researching this question, I discovered that the Young's modulus of carbon fibre reinforced plastic is around 150 GPa which puts it somewhere between brass and beryllium copper.
Well I thought it was interesting anyway