Hi 01svtL,
While bedding isn’t my area of expertise … you can see some general comments about featherbeds in post #6 here.
Down lasts longer, and and is more “comfy” and less “crunchy” but it compresses more and feathers are more resilient and don’t compress down as much (although they don’t retain their loft as well as down in the long term). Both can sleep warm … especially if you have a down comforter as well.
The fabric needs to have a tight enough weave so that any small feather quills don’t poke through the material and the down and feathers needs to be washed in production well enough that there are less issues with smell and allergies from dust mites. Some suppliers have return policies if you discover that you are allergic to their product but most allergies are not to the feathers themselves but to the byproducts of the dust mites that they can contain. An actual feather allergy can be tested with an allergy test.
Both can take some maintenance and need to be protected from any buildup of moisture (which can damage them quickly with mold and mildew) and body oils (which will damage them over a longer period of time). I would also suggest a separate cover that can help with feathers poking through and can also be removed and washed.
Overall they are more for “feel” and outside of cushioning pressure points don’t provide the same level of pressure relief as foams and aren’t nearly as “supportive”.
Phoenix