Back when I tried sidebery, there was some weird issue where either shift-click or right clicking didn't work on mac, and that turned me off. I just tried it again, and both work fine now.

One other feature that is nice for me is the ability to collapse the sidebar to just the tab icons. It's a nice middle ground between being able to see what I have open and getting a full screen experience.

TST and Sidebery are both fantastic extensions, I don't think they do anything wrong. For whatever reason though, the FF native implementation worked for me where they didn't