@leocg To me vertical tabs are the better option because I need more vertical screen real-estate than horizontal. Most websites waste a lot of horizontal real-estate, and having a minimized vertical bar is better because I can free up significant space on the top of the screen and the screen feel clutter free. Specifically Edge, has exactly what I need, but I am sticking to opera because of the other experiences.
Vertical tabs is just a quality of life change which will greatly improve UI of Opera!