Hi Mic,
Assuming that you choose the same type of latex for both (100% natural Talalay) … how they compare would depend on the type and firmness and thickness of the latex layers in each mattress and on the options you have after a purchase to rearrange or exchange the layers. If both used the same type, thickness, and firmness level of latex in the top 3" and the bottom 6" was also the same type, blend, and firmness of latex then they would be closely comparable (see post #2 here about the difference between two 3" layers and a single 6" layer of latex).
Other differences would include the details of their return and exchange policies and their cost.
I would always check with the manufacturer to confirm the details but I believe that the SleepEZ organic uses organic cotton and wool in their cover for the organic version and Arizona Premium uses bamboo (which is high quality semi synthetic fabric) and natural wool in their cover. 100% natural Talalay doesn’t have an organic certification (you can read more about organic certified latex in post #6 here).
You are certainly looking at some great options and when you are down to finalists that are between “good and good” then your final choice (see post #2 here) will really depend on “best judgement” based on your conversations with each of them and on all the objective, subjective, and intangible parts of your personal value equation that are most important to you. As you mentioned … I think highly of both of them and they are both members of the site and either one would make a great quality/value choice.
Phoenix