What did Firefox that Vivaldi does better?

So far:

• No AI slop
• Lower CPU usage
• Broader set of extensions (old Chrome + Chrome V3 both supported)
• Nicer interface with actually configurable sidebar
• Configurable keybinds for everything
• Mouse gestures

But as I say, I’ve only been trying it for a few days, and there are several others I want to try before I settle on a permanent replacement.