Hi feelhong,
Hopefully you’ve read the mattress shopping tutorial which has all the basic information, steps, and guidelines that can help you make the best possible choices.
There are too many unknowns, variables, and individual preferences involved in choosing a mattress to make specific recommendations about “what” mattress to choose … only “how” to choose (see mattress firmness/comfort levels in post #2 here).
There is more about the different properties of different types of memory foam in post #9 here and post #8 here.
The density of memory foam is the single biggest factor in its durability but any density of memory foam can be made in firmer or softer versions. Having said that, lower density memory foam will often (but not always) tend to feel softer for most people and in most conditions than higher density memory foam. In addition to this the thickness of the memory foam, how it responds to heat, humidity, and pressure, and the firmness of the base layer along with all the other layers and components and the design of a mattress will all affect how a mattress feels and firmness is so subjective and depends so much on each person’s body type, sleeping positions, and individual sensitivities that what feels firm to one person may feel soft to the next. It can be very subjective … especially with memory foam.
You are certainly in a weight range where 4 lb or higher memory foam would be a suitable material in terms of durability but the mattress that is “best for you” is the one that is the best match in terms of PPP (Posture and alignment, Pressure relief, and Personal preferences) and all the other parts of your personal value equation that are most important to you.
They are just different memory foams made by different manufacturers. You can make meaningful quality/durability comparisons based on the density of the memory foams but when you can’t test a mattress or material in person you will need to talk with an online retailer or manufacturer that uses each one to find out more about the specific properties or response of the memory foams they use or the mattresses that they sell. A knowledgeable retailer or manufacturer will know more about how their mattresses and the materials they use compare to others they are familiar with than anyone else.
Rocky Mountain Mattress has some videos here about the Sensus, Aerus, and Bayer memory foams that may give you some idea of how they differ.
Phoenix