Take the car and enjoy the drive. Big Sur is one of the most beautiful sections of coastline in the world and nearly as nice is the stretch of Hwy 1 through Sonoma county. Most of the places to pull over and enjoy the views are too small for a long RV. Plenty of B&B's and small hotels along this route and much nicer than the majority of places where you can park a large RV with hookups.
The out of pocket cost will be the same either way so make it a fun trip and take the car and use the many resources like Tripadvisor.com and Yelp.com to find places to stay and to eat.
Best time to go is right after Labor Day. Not commonly known but along the coast the warmest weather is usually in September and also the sunniest.
