I personally prefer to use tabs in the traditional way (i.e. at the top of the browser) vs the vertical tabs on the sidebar. That said, when you have a large number of tabs open, the tabs resort to showing only the favicon of the site and continuing to compress smaller and smaller until they are virtually unusable.
In Safari, there is the option to "Always show website titles in tabs" which prevents this from happening. A large amount of tabs being open causes the tab list to be scrollable, so tabs no longer are too tiny to work with.
Here is a screenshot of the problem in Orion:
Here is a recording of what I mean by how Safari handles it:
I'd love to see something like this implemented in Orion, making the traditional tabs more usable when you have a large number of them open.