Follow up vispring mattress question

Hi you answered my previous question about the Dartmoor superb at John Lewis. I have now also tried the
HAnbury superb now as a soft finish which also seemed comfortable. The HAnbury is more expensive so can you please advise whether you think the higher cost is worth it, if there is any reason I should avoid a soft mattress as I do suffer from a bad back at times , and what the equivalent would be in your range , as I like the guarantee you offer
Many thanks