it varies greatly, but I mainly use "lmao"
lol is usually to prevent using lmao too much, or when something is only mildly funny
"haha" is usually to be sarcastic or to come across to be more friendly
"bahahaha" is a rare thing for me to use, but idrk why I use it when I do
You know you're funny when I type any in all caps, especially lmao