Hi there, I thought I'd report back on this. The Rainbow Dust Edilbe glitters arrived yesterday. I ordered a dark colour (red) and a light colour (pale pink) to see if that affected how glittery they are. I thought I'd do a comparison of inedible (non-toxic/disco dust) glitter, edlible Doric glitter (that I already had) and the new Rainbow dusts.
As you can see from the photo I couldn't do a direct comparison with the Doric because they don't do a red (they don't really do any deep, dark colours).
Obviously hands-down non-toxic is the sparkliest (we already knew that). The Doric is OK for the pale colours and does look slightly sparkly when you first put it on due to the shellac. The Doric is a mix of two different types of particle, the coloured ground rice and then the tiny flakes of shellac. The problem with the Doric is that the rice part quickly gets absorbed into the buttercream and it deadens the initial 'sparkle'. This happens even with buttercream left to set or crust.
The Rainbow Dust I would describle as shiny rather than sparkly - it does shine when it catches the light. It is made with gum arabic (like homemade glitter), but the base colour they have mixed it with (at least in the red and pink) is not a metallic-type colour.
Also the particles are larger and less uniform than the disco dust so I think this has a big effect. i.e. the smaller the particle the more light will be reflected as there is more surface area.
I'm afraid I haven't had time to make homemade as I'm slammed with orders leading up to Christmas (aren't we all!), but if I get chance I'll make some and compare again.
In conclusion, I would say the closest to disco dust is the Rainbow Dust Edible, but it really isn't as sparkly as 'real' glitter.