For me, Vivaldi has 2 major advantages in comparison with Firefox and Chrome, which I also use.

One is that Vivaldi can be controlled with mouse gestures. Mouse gestures can provide a much more convenient user interface for most GUI programs (by avoiding to switch your hand between mouse and keyboard), but unfortunately very few programs have been using them.

The other is even more important for me. The Vivaldi command to print a Web page frequently functions correctly, i.e. what is rendered in the printed file is the same as what the browser renders on the computer display.

In contrast, both Firefox and Chrome almost never render correctly a printed Web page, even if they render it correctly on the display. In Firefox and Chrome the printed page is usually corrupted, with various graphic elements scaled and moved in a different way than on screen, so they overlap over each other.