Tree Style Tabs work well, because screen estate is not wasted on 16:9 and 16:10 style displays. Web browsing is mostly reading task and because of usability, line length cannot exceed a certain width. Thus, there is more screen estate horizontally around the page than vertically on top and bottom of the page you are reading.
I liked vertical tabs on my main monitor where there is plenty of space. But on the laptop, especially with using split screen i got too crowded. I have since made the tabs completely invisible and just navigate trough them with the Vimium extension.
This has some quirks because of the limitations a browser extension has, but I now much prefer to just use keyboard shortcuts and search to jump to tabs.
There is the issue of pages which are designed only for very wide screens and for mobile. In between screen sizes will cause the main content to be annoyingly skinny, if it isn't totally unreadable. These sites are relatively rare, thankfully.
