The short answer hinges on one thing only. If you are going to walk down the gorge, the bus is almost a must. If you are only visiting the hamlet, the car works, with caveats.
Walking the gorge: take the bus
The gorge runs downhill only and you leave by sea, so you never return to the start. Leaving a car at the top means coming back later for it. And the 355 bus ticket from Santiago del Teide is one of the documents required at the access control. The bus solves the return and a requirement in one go.
Only the hamlet: car, carefully
For the hamlet and its viewpoints the car gives freedom of timing. But the Masca road is narrow and full of tight bends, and parking in the village is very limited and fills up early. Go first thing, park only in marked areas and do not block residents’ access.
Decide in 30 seconds
Walking the gorge?
Yes → 355 bus. Most practical, and the ticket is required for access.
Only the hamlet, and an early riser?
Car, arriving early. By mid-morning parking is already tricky.
Only the hamlet, no wish to rush?
Bus. You skip the winding road and the hunt for a space.