Long story short, on mobile your fingers are always reaching out the bottom half of the phones much easier than the top half.
The layout Opera mobile has is a lot easier to navigate, particularly moving around tabs and main features. The Chrome-like navigation is a lot worse.
Also when navigating tabs the horizontal distribution where you navigate left/right to move around tabs is a lot clearer (since most page backgrounds are white, the borders of the tab borders are white and the background of the UI is light, it’s almost indistinguishable what’s tab content and what’s browser UI.
Just use Opera mobile and Brave or Chrome and you’ll understand the major difference!