Type of mattress I need

Hello
Can you advise on the best type of mattress for us?
We currently have memory foam, but it’s old. My husband likes firm mattresses (ideally foam). I like medium to firm. I’m 5ft 6, 8 stone and he’s 6ft and about 12 stone.
I’ve read natural materials are better than the synthetic ones on the market. Is that correct?
Thanks!
Natalie Rowe.