I *think* I started with default. Then for a brief period (maybe a year, or a particular game, or something) I played inverted. Then at some point I switched back to default and that's still where I am. I don't understand the logic behind inverted*, I want the camera to move in the direction I press the stick. I don't have to mentally invert it in my head to hit the stick so the game can un-invert it to convert it back to the desired behavior.
Specifically, I don't understand people who do invert Y but don't invert X. If you're going to use the weird " it makes sense because I'm tilting the back of the imaginary head/camera one way to make the front of the head/camera go the other way" kind of logic then I don't understand why you wouldn't do it on both axes. But I've known several adamant Y-inverters who, when I say something about inverting X, are basically like, "....but that's weird, though." ¯\_(ツ)_/¯