The short answer
Buy the Zinus Green Tea for the bed you sleep in every night. It states fiberglass-free construction, names CertiPUR-US foam and an OEKO-TEX certified fabric, and adds a cooling infusion the Amazon Basics bed does not have. On the criteria this site exists to apply, it wins on every one that is actually documented.
Buy the Amazon Basics for a spare room, a teenager, a rental, or a short-term fix while you save for something better. It is a competent certified-foam mattress at the lowest price we would recommend at all, and there is nothing wrong with that job.
The specification that separates them
Fiberglass is used in mattresses as an inexpensive way to meet flammability requirements — usually a woven sleeve around the foam core, under the cover. It is not a scandal in itself, and a fire barrier is a legal requirement, not an optional extra. The problem is what happens when the cover comes off: the fibers can migrate and are genuinely miserable to clean up.
The Zinus listing states the build is fiberglass-free. The Amazon Basics listing does not address it at all. We mark unstated specs “Not published” rather than assuming the worst, and it is worth being careful about what that means: silence is not proof of fiberglass. But it is also not the reassurance a stated claim gives you, and when one bed at the same price will put it in writing, there is not much reason to accept the one that will not.
The other point worth making, because it is the single most common misreading we see: CertiPUR-US does not cover this.It certifies the flexible polyurethane foam — restricted substances, low VOC emissions, restricted flame retardants — and says nothing about fire barriers, which are a separate component. Both beds carry it. It settles nothing here. The certification decoder lays out the scope of each badge, and our fiberglass-free page explains how to check any mattress yourself.
Materials and feel
The Zinus adds green-tea and charcoal infusion plus a cooling cover to a conventional memory-foam build. Infusions are marketed harder than they deserve — they do not turn memory foam into a cool-sleeping material — but combined with the cover they do take the edge off the heat build-up that is memory foam's oldest complaint. The Amazon Basics uses a cooling gel layer for the same purpose, so neither bed ignores the problem.
Both are medium-firm, and both are all-foam, which means both behave the same way over time: they soften with heat and with use, and they soften first under the heaviest part of you. That is the honest limitation of every all-foam bed at this price and it applies equally to both. If you are heavier than about 230 lb, or you sleep on your back and know from experience that foam lets your hips settle, the answer is not either of these beds but a coil hybrid — the Zinus foam-versus-hybrid comparison covers that fork directly.
The fabric certification nobody mentions
The Zinus listing also names OEKO-TEX certification for its fabric. This is a smaller point than the fiberglass one but it is not nothing, and it is almost never discussed at this price. OEKO-TEX STANDARD 100 tests every submitted textile component against a long list of harmful substances, with stricter limits the closer the fabric sits to skin.
A mattress cover is about as close to your skin as a textile gets, for a third of every day, and it is the one layer of a mattress you are in direct contact with. So a certified cover is a reasonable thing to want, and the Amazon Basics listing does not claim one.
What both beds are missing
Neither publishes a sleep trial. Neither publishes a foam density figure, which is the number that would actually tell you how long the bed stays supportive. Both are twelve-inch all-foam builds with a comfort layer considerably thinner than what you get one tier up.
That is the shape of this whole price band, and it is why we treat the documented specs as decisive: when two beds are equally opaque about the things you cannot see, the one that is transparent about the things you can check earns the benefit of the doubt. If you want a bed that publishes more of its specifications, that starts a tier higher — the DreamCloud against the Sweetnight CoolNest covers what the next step up actually buys.
Making either one work better
Both beds respond well to the same two cheap adjustments. If the surface reads too firm at your shoulder and hip, a three-inch high-density topper fixes that without touching the support underneath. And whichever you buy, a knee pillowdoes more for lumbar alignment per dollar than the difference between these two mattresses — the Cleveland Clinic's own guidance is a pillow between the knees for side sleepers and under them for back sleepers.
