If you have sensation, a moderately dense foam cushion is probably going to provide the best comfort and portability for you and is much more economically priced. Cushions are expensive, and mostly covered under medical insurance. Cushion covers can sometimes be problematic. Sheepskin is sometimes a real culprit. With these, one should use only the covers that come with the cushions.
Mattresses are also an area where a great deal of confusion exists.
In general, comfort and support are of great importance. If you get a sore. This is where it's really important to have a good understanding of one's skin and how it reacts to pressure. Unfortunately, while that may keep the pressure off the sore, it actually cuts off the circulation to the sore, and so makes things worse than if they did nothing at all. If one has a deeper sore, it's even more important to keep the pressure entirely off the area of the sore.