Couples who have different body types will definitely have different mattress firmness needs. They may also have divergent material needs as well. If your body weights and sleeping positions are not that incompatible, you may be able to find a compromise on firmness level and material. If you can’t, you’ll have to do a split king mattress to sleep in the same bed.
A split king size mattress will allow you to put two separate twin XL mattresses in the same standard king size bed frame. These beds let you choose your own construction and foam firmness level. You can also pick your own adjustable base settings and even mattress thickness, all while sleeping in the same bed.