I can't speak to that 100% but I do remember trying both (albeit briefly) and ultimately settling on Sidebery. Looking at the addons page, TST dev actually mentions Sidebery and a few others in their Developer Comments.

*Edit: It seems to imply that Sidebery is a tree addon with extra features. The most notable of which that sold me was the snapshots. I kept losing all my (~200) tabs if I closed Firefox improperly on my Macbook which was not fun.