Here's why it works and some possible variations:
* Grammatically Sound: The sentence follows the basic Subject-Verb-Adjective structure. The subject is "The difference (that the haircut made)," the verb is "was," and the adjective is "impressive."
* Clear Meaning: The parenthetical phrase "that the haircut made" clarifies which difference is being discussed, specifically the change caused by the haircut.
* Emphasis: The word "impressive" emphasizes the significant and positive impact of the haircut.
Possible Variations (depending on the desired nuance):
* The difference the haircut made was impressive. (More concise, equally effective)
* The haircut made an impressive difference. (More active voice, also good)
* The change after the haircut was impressive. (Simplifies the sentence slightly)
* The haircut's impact was impressive. (More formal)
* Wow, the haircut made a huge difference! (More informal, emphasizes the magnitude of the change)
In short, your original sentence is perfectly fine. Choose the version that best suits the context and the tone you want to convey.