They're all equally funny:
Sonny Forelli: His temper and his first line in-game when he talks too fast that he slurs his words.
"Tommy Vercetty? Hah! sh*t! Didn't think they'd ever let him out!"
"Hah! Surgjette! Dindelelelemau!!!"
"WHERE'S MY MONEY TOMMY!!!!!!!!!!"
Big Smoke memes.
"All you had to do was follow the damn train CJ!"
"I'll have two number 9s..."
Roman: His blind optimism is something else.
"Let's go bowling!"
"We should eat together!"
Chan Jaoming: Guy is so retarded he falls for Huang's blatant sarcasm.
"...but I've got leadership in my genes."
Huang: "I'm sure you've got a lot of things in your genes." (Implying that his drug abuse made him stupid)
Zhou Ming's ego is so huge that thought he can walk on water like a god.
This is the hardest I've laughed on a Rockstar Game by far...