I started from my home in Mountain View, CA early in the morning at 6 AM and reached Yosemite Park (Oak Flat Entrance) by 9:45 AM. I took Highway 120 to get there. This is a mountainous route. I had to drive slowly and carefully. On the second and third day of my trip I entered the park via Highway 140 (Arch Rock Entrance) and most of the highway was a flat road and for about 10 miles the road runs parallel to the Merced River. I wouldn't pick one over the other. But, I learned that highway 140 is the best route to Yosemite Valley in winter and you may not even need snow chains. Other ways to enter the valley include via Highway 41 (south entrance) and Tioga Pass entrance (open only in summer). Guess what! You can travel to Yosemite Valley by train (Amtrak). I thought of going there, but did not do it because I had to change trains at two stations to get there and also because rental cars are not available in Yosemite Valley. I might try this, if they run trains in winter.