I also use invert Y, as does one of my friends. Other friends, the same age, don't. Honestly, I think it's purely conditioning, I don't see any reason why either would objectively be better. You could probably "reprogram" your brain to use the other setting, although it would probably take a while to equal your previous skill.

It's probably a combination of the fact that we played 3D games (flight sims, Descent, etc.) before the mouselook FPS was invented, and we grew up on Joysticks before 3D games with mouse control became the norm. Those friends who don't use inverted Y got into games later than us.