As far as I understand, Unity is mostly just a Gtk-based desktop environment similar to Cinnamon, but with the Unity shell and launcher, and the global menu.
As a long-time Mac user I always liked the global menu, but it was just such a pain to always have to patch Gtk to get it to work, and in the end it isn’t such a huge improvement to my quality of life that I think it is worth the trouble. It is nice that Unity takes care of this for you. That said, and I hate to admit it, but I think Gnome actually is more stable than Unity, mostly because there is so much more financial backing for it, so it is hard for me to recommend using Unity unless you really just love the aesthetics of it.