Cotbed mattress recommendation

Need some advice on cotbed mattresses. I’m in the UK looking at the mamas and papas premium dual core one £100ish (currently £100 off) or the obaby foam one £39.99. The foam one I had with my first but the dual core one is apparently recommended to be better and foam ones are good for grandparents who have them now and then? Dual core one felt so hard in the shop for baby side but it does flip over for a softer side from 1 year old. Just wondered what people would recommend as the best cotbed mattress? Thanks