Often, anime ops spoil the story by showing clips or images that hint at major events or twists. This can happen if the creators aren't careful in their editing. For example, a character's transformation or a big confrontation might be shown too early.
For me, it depends on personal preference. Some people love the manga's original art and story pacing, while others enjoy the animated action and sound effects of the anime.
The opening of 'Fullmetal Alchemist: Brotherhood', 'Again'. It starts with the two brothers, Edward and Alphonse, in their search for the Philosopher's Stone. The opening is full of scenes that represent their adventures, their battles against the Homunculi, and their quest to regain their normal bodies. It really does a great job of setting the tone for the story.
The Haikyuu anime concludes at a specific chapter in the manga. However, the manga continues beyond that, offering additional plot developments and character arcs.
The Haikyuu anime has some variations in terms of pacing and the order of events. For example, certain matches might be presented in a slightly different sequence.