Cars, no contest, and I live in an area with TERRIBLE mass transit. I live in a small town just west of San Jose in Silicon Valley, and in order for me to get anywhere, I have to take a 45 min bus ride (the only bus that comes into my town) into Sunnyvale and from there either catch another bus or Caltrain to get where I'm going, and often times another bus, Muni or Bart after that.
That said, I would still rather keep my Internet than gain a car. Safeway delivers for free, I no longer need to go to Blockbuster to get new content, and I can (if I chose) work completely remotely.
Living without a car sucks, especially in California where public transportation is a joke, but its still better than living without internet.