I chose Zotero because:

• it’s free (unlike EndNote)
• it’s open-source with integration for a wide range of devices/apps
• it had better reviews than Mendeley in the areas I was interested in (data privacy, citation accuracy and integration with Word – Mendeley comes out better if you are interested in higher storage limits and social collaboration/ recommendation functions). This was a very comprehensive review I found, and seemed to back up what I had seen elsewhere.
• it has two levels – the more basic ZoteroBib, which is just a citation generator ,and the more comprehensive Zotero, which is a citation manager. This allows me to use the same tool at different levels with different year groups.

It would be interesting to hear what others are using and why – and how you are getting on. I’m fairly early in my journey with these tools, but already feel we have made a huge leap forward from the Word tools (not least because I can now  easily support footnote referencing, where I couldn’t before, and because Chromebook and iPad Pro users are not excluded).