Hi sfs244,
There really wouldn’t be any exact equivalents because the designs of all the mattresses you are looking at are different but you can read a little more about the different ways that one mattress can “match” another one in post #9 here.
In terms of quality/durability … any mattress that used the same type and quality of materials would be comparable but this would have nothing to do with the feel and performance of the mattress in terms of PPP (Posture and alignment, Pressure relief, and Personal preferences).
If you are trying to match one mattress to another in terms of PPP then if the layers or components of each mattress are different you would need to “translate” one design into the other which can be a very subjective and intuitive process. The best way to do this would be to first find out the specifics of a mattress you are trying to approximate (you would need to know all the quality specs and the comfort specs of all the layers and components and some of these may not be available to you) and then have a more detailed conversation with an online manufacturer about which of the options they carry they believe would come closest to the mattress you were using as a reference point for your body type and sleeping positions (see mattress firmness/comfort levels in post #2 here). They will know more about matching their mattresses to the needs and preferences of their customers or how they compare to another mattress where you know the details of the design and materials inside the mattress than anyone else.
Both Flobeds and SleepEz are members here which means I think highly of both of them and they compete well with the best in the industry in terms of their quality, value, and service.
Some of the better options and possibilities I’m aware of in the New York City area are listed in post #2 here.
Phoenix