I've found that some OPDS catalogs have multiple downloads of the same filetype, but optimized or formatted in different ways. The Title of the download is much more descriptive in this case, so I thought it would be better to display the title if available.
The OPDS catalog at https://standardebooks.org/opds is a good example. Note how entries in https://standardebooks.org/opds/new-releases have three different epub downloads, titled "Recommended compatible epub", "Advanced epub", and "Kobo Kepub epub".