Why is the first sentence better than the second one?
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Used with a noun or verb stem to form i-adjectives to express the meaning "feels that way" or "has the tendency to".
Used with nouns that express colors to express the meaning "has that color/characteristic" or "close to that color/characteristic".
This medicine tastes like chocolate.
When used in this form, N2 (our 車) is described by giving an example of something (N1, our 黒) that bears resemblance. In this example sentence, you can see that the medicine bears resemblance to chocolate (in its taste).
Since "black" bears no resemblance to a "car" in this sense (the color "black" doesn't have the shape of a "car", etc; plus, using でした versus a verb that could possibly connect the "car" and "black" with みたいな better), we cannot use みたいな in this way and therefore っぽい is the better choice.