I heard lower wisdom teeth are harder to extract. Is that true?

Yes, extracting a lower wisdom tooth is generally more difficult than an upper one. The lower jawbone is denser, the tooth is often impacted lying on its side, and it sits close to the jaw nerve (the inferior alveolar nerve), so the risk of altered sensation has to be assessed beforehand. At our clinic we take a panoramic X-ray first and, for an impacted wisdom tooth close to the nerve, confirm its position with a CT scan before planning the extraction. However, an upper wisdom tooth can also be difficult if it is deeply impacted or close to the maxillary sinus.