Should you base yourself in Muscat or Nizwa?
Use Muscat to arrive, adjust and see the coast; use Nizwa when the trip turns inland. Sleeping in Muscat every night can make Oman look easier on paper and harder in the car.
Answer
Muscat is useful and worth time, but it is not the best base for everything. It works for the mosque, Mutrah, the coast and a gentle start. Nizwa works when the itinerary becomes forts, souqs, villages, Jebel Akhdar, Jebel Shams and inland drives. The map makes some day trips look manageable, but repeated returns to Muscat can turn scenic Oman into a commute. If you want the trip to feel less rushed, change bases when the landscape changes.