The black pill is the logical one to take. It’s basically a get out of death (or jail, I suppose) free card if you can use it at the right time. Unfortunately, most people don’t speak the language or have a passport that would allow them to leave the country. So you might have problems there.
Changing eye color at will would be cool as well, but not as useful in an emergency.









I’ve not looked up the actual elevation differences, but I think that you would most likely survive with a bout of vertigo. People have no issue surviving cabin pressure loss in an aircraft, which is a larger difference in pressure than you would probably see.