Hi carreaue,
Both the Christeli and the Restava use good quality materials with 3" of memory foam over a good quality base polyfoam and have no obvious weak links. The Christeli has 3" of 5.3 lb memory foam and the Restava has 2"of 4.2 lb gel memory foam and an inch of 5 lb memory foam so the Christeli has slightly higher quality/density memory foam in the top layers. Both would make good choices in terms of quality/value as long as they were suitable in terms of PPP (Posture and alignment, Pressure relief, and Personal preferences).
When you have eliminated all the worst options (which you have) and you are down to final choices between “good and good” (which you are), then there are no longer any obvious “better and worst” choices except based on the specific personal criteria and tradeoffs that are most important to you. Post #2 here about making final choices may help.
Phoenix