Hi redwinger,
While I can’t tell you which specific mattress to buy because only your own personal testing or sleeping experience can tell you which mattress is most suitable for you … I can tell you that the Christeli Palais Grand Royale uses very high quality materials that are higher quality overall than the Tempurpedic Grand Bed.
The Grand Bed includes the following layers …
2" of 7 lb memory foam
1.2" of 5.3 lb memory foam
4" of 5.3 lb memory foam
8" of unknown density polyurethane base foam (two convoluted 4" layers).
The Christeli Palais Grand Royal has the following layers …
1" of 8 lb memory foam (NOTE ADDED: they are now using 6 lb memory foam)
4" of 5.3 lb memory foam
6" of 100% Natural Dunlop latex
3" of 5.3 lb memory foam
As you can see the Christeli uses the same or higher quality materials … particularly in the base layer which uses talalay latex instead of polyfoam which is a much higher quality and more adaptive and responsive material. The Christeli also has the option of using different configurations because you can use the base latex mattress with one or both toppers on top and with or without one of the toppers on the bottom to create different “feels”.
Christeli would be the best source of information about how close any of the possible configurations of their Palais Grand Royal matches the feel and performance of the Tempurpedic GrandBed and they also have a good exchange policy and a good return policy as well (if you purchase the $29.95 Signature return option) just in case you don’t agree with their assessment because each person’s experience on a mattress is subjective and may not agree with someone else or even the majority of other people.
The only caution I would have with either mattress would be that thicker layers of memory foam (such as in the GrandBed or with both toppers on top of the Grand Palais) can be risky for some people because memory foam can continue to soften over the course of the night in response to temperature, humidity, and time so some people may find that they start off the night in good alignment but wake up in the morning out of alignment.
In terms of durability they would be close to equal (they use similar density foams in the comfort layers). Latex is more durable than polyfoam but the support layers of a mattress are not normally the weak link in a mattress in terms of durability so the advantage of the latex support would be more about performance than durability.
They also sell the Lux Estate which also uses the GrandBed as a reference point but only has one removable topper and has 2" of 8 lb memory foam (now also 6 lb) on top similar to the GrandBed.
If your local testing indicates that the Allura is a better match for you than the GrandBed in terms of PPP (Posture and alignment, Pressure relief, and Personal preferences) then Christeli also has their Charleston which uses the Allura as a reference point and by flipping this mattress you can create a slightly softer or firmer feel on this as well (each side of the polyfoam base layer has a different firmness level).
So I would use your testing and personal experience to choose between the GrandBed and the Allura and then use your preference between them along with your conversation with Christeli and the value you place on the different customizing features of each mattress as the guideline for making a choice that is the best match for your personal value equation.
Phoenix