Bookends is absolutely the most powerful reference manager available. Nothing comes close. It has a bit of a steeper learning curve at first but it’s worth it. Its only downside is that it’s nowhere near as good as Zotero at getting metadata for books and older journal articles. If you only need to use PubMed, etc. that won’t be a problem but anything published more than 15 years ago will probably have imperfect metadata. This limitation can however be overcome: How can I use Devonthink 3, PDF Expert and Zotero together? - #3 by prc