They are equal if you consider the space occupied by stacked tabs. If you want more space for the content or equal space for the content of stacked and non stacked panes, you can resize the split to suit your needs.
I mean the same as the sliding panes plugin used in the early version (like v15.), in order to see the content, it may hide some of the tabs. But if you want to see the tab, you could just scroll the pane to the left or right, then the tab title would show up.
If you are working on some pages, I think the most important thing is to focus on the content. If so, showing the tab title may not be that important.