For me it was performance. Google Chrome consistently couldn't handle the tab loads I would put on it after around 2022, despite my computer not really showing signs of degradation.

Since switching to FF, I can run the same amount of tabs with almost not hiccups or stuttering - what I'd experience with Chrome. Hell, Chrome would crash randomly and I'd lose all my tabs and would have to reload them.

Plus, sometimes to fix Chrome's poor performance I'd shut the program down entirely, upon re-launch the browser wouldn't even remember all of the tabs/windows I just closed (it used to). So, if I was doing research on something, Chrome would just not open certain windows back up after a hard reset, even if I CTRL + SHIFT + T and I check history. Madly infuriating.

FF opens all windows and tabs upon hard reset, no questions asked. Plus, the compatibility between PC and mobile is awesome: I can load up a tab from my phone that's on my PC super easily, which makes things useful for when I want to share web content with friends or family.

I seem to have woken up from my slumber of tolerating Chrome, and chose a better service instead.