What's your preferred definition for the edge of space? Which of these makes the most sense to you?

- the edge of the stratosphere, below which 99% of the Earth's atmosphere is found, at about 50 - 60 km?
- the U.S. Air Force and now also NASA's definition at, from what I can gather completely arbitrary, 50 miles or 80 km?
- the Kármán line, where 99% of the lift of a craft are provided by the Kepler force as opposed to aerodynamic drag, at about 91.5 km?
- the rounded up value from the Kármán line by the FAI and formerly the NASA at 100 km?
- a proposal that uses the lowest orbit where a circular revolution around the planet without propulsion can be completed, which is roughly 150 km?
- the top of the thermosphere at around 600 km?
- the altitude of a geosynchronous orbit at 35,786 km?

Or can you come up with a yet another definition?