In terms of what people say and do on the platforms, which do you think is worse? I have been a part of both. I always preferred Twitter because it was less personal but when it started getting very political and people started trouble with each other off the platform using it as a tool to ruin lives, I hopped ship. I can't be part of a platform where this is acceptable behavior and nothing is done about it.
As for Facebook, I feel like it is mostly used by people who are 45+ now. Not one of my friends are on there anymore. I stopped using my account back in 2015 and don't miss it. I know back then, people got into trouble with each other using the site as a means to cheat on spouses and partners. Then fake news and false facts was an issue for a while. It seems like people who don't know how to communicate online use Facebook.