What's the difference between the Artisan Natural and Bespoke 004

Hello,
My husband and I are looking for a new mattress. I like the idea of a natural mattress because of the benefits it reportedly brings to the quality of your sleep. However, my husband is less concerned about the mattress contents and more about price. We are therefore now debating the Artisan Natural and the Bespoke 004 and wondered what difference does the 15% natural material make in the Bespoke 004?
Many thanks.