Hi jarnholt,
That would depend on the person and would really be something where you would need to be deciding between two specific mattresses so you can take into account the specific pros and cons of each one and which of them was the best match for all the parts of your personal value equation that are important to you.
Latex is a higher performance material than polyfoam but of course it’s also more costly and higher performance would also need to translate into something you can “feel” in real life. It is also more durable but the support core isn’t usually the weak link of a mattress so durability may not be an issue in either case … particularly if the latex/polyfoam hybrid is two sided. I think in the end each mattress needs to be evaluated and compared to another specific mattress that is one of your “finalists” so that you can take into account how each mattress feels and performs for you in terms of PPP and all the other parts of a mattress purchase (not just the mattress itself) that are important to you so that the comparisons between them are more specific rather than generic.
In theory I think latex is a superior material to polyfoam and if cost was no object (even though it usually is) I would personally choose it over polyfoam but that’s only if everything else was equal which is rarely the case between two mattresses. There are so many other parts to a mattress purchase (such as PPP and in this case some of the benefits of a two sided mattress vs a one sided mattress) that theory isn’t usually the most effective way to make these kind of specific choices. Once you are down to final choices that are between “good and good” then it’s a matter of comparing the pros and cons of each choice and the tradeoffs that are involved in each rather than a “better worse” comparison. In other words … which one is “best for you”.
Polyfoam that is made in North America or is CertiPur certified normally doesn’t have any significant issues in terms of VOC’s or offgassing that would affect most people but for those that are more highly sensitive or people with medical conditions such as MCS (multiple chemical sensitivities) then latex seems to be better tolerated than polyfoam which in turn would be better tolerated than memory foam … but this is based on overall “averages” and is not specific to any particular person. Once you are down to smaller percentages of the population that are “outside the norm” then each person can be unique in terms of what they may be sensitive to.
I would also keep in mind that warranties are more about marketing than anything else and don’t predict the useful life of a mattress or how long you can expect to sleep on it before replacing it (see post #174 here). Neither of these mattresses have any weak links that would present a durability issue. There is also more about the factors that can affect durability and the useful life of a mattress relative to each person in post #4 here and the posts it links to.
The most effective approach is to buy a mattress that your testing (using the testing guidelines) indicates is a good match for you in terms of PPP. I would avoid purposely buying a mattress that is either too firm or too soft. If you buy a mattress with the specific idea of adding a topper and you haven’t tested the specific combination you are only adding another variable that can be almost as difficult to “get right” as buying a mattress in the first place. Having said that … I would avoid buying a mattress that is on the very edge of being too soft for you because in these cases even a little bit of softening can put you “over the edge” and the mattress may no longer be suitable for you to sleep on even though it’s still in good condition and would be fine for someone else (see post #2 here). This isn’t a durability issue (especially with latex or other high quality and durable comfort layers) as much as a suitability issue and choosing a mattress that is too soft in the first place.
SleepEz is one of the invited members of this site which means that I think very highly of them and that they compete well with the best in the industry in terms of quality, value, and service and they would certainly be well worth talking to and including as one of the better options available to you.
Outside of PPP … a mattress is only as good as its construction and the quality of materials and components inside it and SleepEz uses latex (including options for different types of latex such as 100% natural Dunlop, blended Talalay, and 100% natural Talalay) which as a group are among the highest quality materials available in the industry. Most of their mattresses are also component mattresses where you can choose the firmness of each layer in the mattress and can either re-arrange the layers or exchange a layer after a purchase if you discover you need to fine tune your firmness choices after sleeping on it.
Phoenix