The band is pretty much the same in both bras. The 36FF bra has bigger cups.
Types of Bra & Bra Style Guide
Freya Women's Deco UW Moulded Plunge Bra, Black, 28D
Deco Black Moulded Plunge Bra from Freya
28G - Freya » Deco Moulded Plunge Bra (4234)
Festival Vibe Deco bra by Freya, White Print, Plunge Bra
80F - Chantelle » Révèle Moi Perfect Fit Underwire Bra (1571)
Freya Women's Deco UW Moulded Plunge Bra, Black, 28D
34F - Freya » Deco Moulded Plunge Bra (4234)
Freya » Deco Rebel Moulded Plunge Bra (4234)