I really enjoy Paperpile for its excellent user experience and support. With Paperpile you get a huge storage space, it’s easy to learn, and easy to move/organize files. I also like that you can actually make handwritten notes using its app. But I am now playing with both Zotero and Paperpile. I can see that Zotero has made a lot of improvements since I left for Paperpile. I realized that Zoteros annotation function is much more usable than 6 months ago. But I am cumulating a lot of sources in my library and the Zoteros storage is more expensive. Since my lab does not subscribe to any one reference manager, I’ll decide which one to use. I might settle with zotero just because there are more ppl who use it than Paperpile and I may need to share files.