Hi miles4,
I would also tend to avoid these two platform bedframes as well along with any others that are in a similar price range that use thinner wooden slats that are easier to break and where the frame itself isn’t particularly well made (read some of the lower rated reviews).
If your budget is extremely restricted and since your mattress has a polyfoam base layer then I would probably choose one of the wire grid platform bedframes that I mentioned in the reference post I linked for support systems rather than the ones that use lower quality wooden slats that are prone to bending or breaking. There are also some comments and some suggestions about wire grid platform bedframes in post #10 here that can help make them more supportive as well if you are looking at some of the cheaper ones that have wider spaces between the wires.
Phoenix