Flying autonomous vehicles can reasonably be energy efficient, and clearly are space efficient (due to the three dimensions that provide plenty of space).

Travel time is the correct property to optimize for my values. I don't want to spend unnecessary time in transit. That's a subjective value, of course.

You can optimize for quality of life, health and short travel times at the same time. Copenhagen might be a good target with current level of technology, not necessarily the technology of future.

I don't care for imposed social interaction due to public transportation. People don't really interact with strangers in public transportation anyway (in my culture that is).