Comparing original dialogue and a dubbed version need not become a contest with a predetermined winner. Both provide access to a film, while potentially conveying intimacy, timing and humour differently. A short scene whose situation you already understand is enough for a useful comparison. When you are also trying to work out an unfamiliar plot, differences between performances are harder to notice.
Give both versions the same scene
Choose an encounter involving two or three people and a clear change: a friendly greeting might become an accusation. Listen to the complete scene in one version and then the other. Switching after every word makes it difficult to follow a performance as it develops. Afterwards, record only the moment when the mood seems to change.
Available language versions depend on the particular release or service. A streaming audio menu lists the tracks you can select, rather than every version ever produced. Check subtitles separately as well. Translated subtitles need not reproduce the exact wording of a dub. When reading and listening together, do not automatically treat different phrasing as a mistake.
Listen to the character's voice
Notice breaths, sentence endings and the gap between a question and its answer. An immediate reply may sound quick-witted; a short hesitation may suggest caution. These qualities can be heard without extensive knowledge of the original language. The precise meaning of a pun, however, needs linguistic context and cannot reliably be inferred from sound alone.
Separate familiarity from a specific observation. A familiar dubbed voice may form part of your memory of the character. That explains a preference without demonstrating a weakness in the other performance. A more informative observation would be that one voice becomes quieter in the final clause while the other maintains its level. You can then ask whether the difference creates uncertainty or resolve.
Translation inside a moving image
A character speaks within a visible action and an available interval of time. Compare the shape of a whole utterance as well as individual words. A compact sentence may replace a longer phrase while preserving the conflict. An outside explanation is most useful when a genuine question about meaning remains, rather than whenever the wording differs.
Finally, hear a passage involving distance: a voice behind a door or a call from across a room. Describe how close or distant it seems in each version without inventing a production history from the impression. Your listening alone does not establish how the track was processed. The comparison is most useful when it identifies an audible choice and explains what that choice does to the scene.