Toggling CSS classes is the most efficient approach for updating multiple element styles because: 1) Browsers optimize class-based style changes better than inline styles, 2) Changes can be batched and handled more efficiently by the browser's rendering engine, 3) Reduces redundant style calculations, 4) Keeps presentation logic in CSS where it can be better optimized. Additionally, using classes: promotes better separation of concerns, makes styles more maintainable, and allows for easier transitions and animations through CSS.