I think, to answer the OP's question, TIFF would be a better alternative, especially because it allows to store a full Works-in-Progress layered version of your images.
If my understanding is correct, "a full Works-in-Progress layered version" produced by PS could not be opened and further processed by any editing software other than PS
. A flattened version could, presumably, be opened by other editing software. Please correct me if I am wrong.