I always use inverted.

I first played flying simulators as a kid, and inverted makes a ton of sense. 3D shooters weren't really a thing yet, so when they became a thing, I kept using inverted controls and it was comfortable.

I can switch, but it takes some getting used to, and my error rate is higher.

That said, when I use a mouse, I want up (forward) to go up, and down (backward) to go down, so the inverted controls are only for controllers w/ joysticks.