I have tried Endnote, Mendeley, Paperpile, Sciwheel and Zotero (back when it was firefox only, which was a long time ago). I currently use and pay for Paperpil

I have tried Endnote, Mendeley, Paperpile, Sciwheel and Zotero (back when it was firefox only, which was a long time ago). I currently use and pay for Paperpile. I found the user experience to be the best for my purposes, mainly the ease of importing articles. The word plugin is hassle free as well. They seem to be pretty competent developers eg Mendeley’s iphone app wouldn’t sync properly for literally years, whereas Paperpile’s app was good from day one. The downside of Paperpile is lock-in to the Google ecosystem (only works on Chromium browsers, although firefox and safari support is coming). There is also no quick way to tag or categorise papers at the time of import from the web, you need to go to the app. Sounds like Zotero is pretty good now though, might have to check it out again.