The 30G bra has a bigger band than the 28G bra. The 30G bra has deeper cups than the 28G bra, but they are about the same width.
Freya Women's Deco Underwire Molded Plunge Bra, Black, 28D at
Thoughts on the Freya Deco Plunge – Let's talk about bras
28FF - Freya » Deco Moulded Soft Cup Bra (4231)
Freya Deco Molded Plunge Bra
28E - Freya » Deco Moulded Plunge Bra (4234)
28E - Freya » Deco Moulded Half Cup Bra (4232)
30FF - Freya » Deco Moulded Plunge Bra (4234)
Comparing a 28E Freya Deco Moulded Plunge Bra (4234) with a 30DD
Moulded Shapes Explained
Thanks to everyone here I made the plunge and bought a freya deco
28DD - Freya » Deco Moulded Plunge Bra (4234)
28DD - Freya » Deco Moulded Plunge Bra (4234)