Both roads are very nice in different ways. The Coast Rd has interesting interpretation stops, no RVs are allowed, the dirt/gravel road is very well maintained and street tires will be fine. The Parkway is the original 101 before the current by-pass was constructed. It takes you through some stately giant Redwoods. I rode both as a circle day ride in 2009. Both take you to Prairie Creek campground if that's where you are planning to stay the night. I couldn't recommend one over the other.