Depends on what you use. Some coatings are designed to be heat barrier. Those work well on the piston crowns to prevent heat transfer to the
oil. Some coatings are designed to transfer heat at a higher rate. They would work well on the chamber walls.
I'v been doing a lot of reading about these coatings. This year I plan to add an anti-friction coating to the piston skirts, and a thermal barrier to the piston crown. Although the other coatings look interesting, I don't think there's enough bang for the buck for my use.