In my own limited experience, Facebook has changed less than Twitter from the perspective of conversation dynamics, to the extent that I now prefer FB, while I used to prefer Twitter.
For one thing, FB is less "flat". On FB, my updates only go to my FB friends, or optionally to "friends of friends". They are the only people who can either see or comment on them. So the size of my friend list has a large effect on discussion dynamics. That grows pretty slowly, so my FB experience hasn't changed too much. On Twitter, I could have a "locked" profile, but the norm is to post publicly, and certain things that are iconic of the platform (like retweeting) don't work if you're locked. There is also no "friends of friends" option, so you're either locked or public.
That wasn't a problem until recently, but in the past year or so, there seem to be a lot of people (sometimes called "randos") using the search functionality, and sending weird, often abusive, replies to people they don't even know, because of a tweet that came up in a search. The "virality" of retweets also accentuates that. Sometimes an offhand comment ends up read by 1000+ people because a chain of people retweeted it, and then there are all these really out of context replies by people who aren't even within three degrees of relationship to me. That can be welcome sometimes, and not welcome other times. Once in a while, if you're unlucky, something you say will get retweeted in a negative context by someone quasi-famous, which results in this weird swarm of mindless acolytes. And some of those acolytes feel the need to dig up your contact information and harass you outside of Twitter as well, even though 30 seconds ago they had no idea who you were, and still really have no idea who you are. These kinds of dynamics just aren't that enjoyable imo, and not worth the effort it takes to deal with them, so I've been using Twitter less.
For one thing, FB is less "flat". On FB, my updates only go to my FB friends, or optionally to "friends of friends". They are the only people who can either see or comment on them. So the size of my friend list has a large effect on discussion dynamics. That grows pretty slowly, so my FB experience hasn't changed too much. On Twitter, I could have a "locked" profile, but the norm is to post publicly, and certain things that are iconic of the platform (like retweeting) don't work if you're locked. There is also no "friends of friends" option, so you're either locked or public.
That wasn't a problem until recently, but in the past year or so, there seem to be a lot of people (sometimes called "randos") using the search functionality, and sending weird, often abusive, replies to people they don't even know, because of a tweet that came up in a search. The "virality" of retweets also accentuates that. Sometimes an offhand comment ends up read by 1000+ people because a chain of people retweeted it, and then there are all these really out of context replies by people who aren't even within three degrees of relationship to me. That can be welcome sometimes, and not welcome other times. Once in a while, if you're unlucky, something you say will get retweeted in a negative context by someone quasi-famous, which results in this weird swarm of mindless acolytes. And some of those acolytes feel the need to dig up your contact information and harass you outside of Twitter as well, even though 30 seconds ago they had no idea who you were, and still really have no idea who you are. These kinds of dynamics just aren't that enjoyable imo, and not worth the effort it takes to deal with them, so I've been using Twitter less.