Tough descision but I would have to say Casino 'cos of Joe Pesci.
Nick Santoro absolutely goes ballistic with his cursing and comments. IMHO his performance was better in Casino than in Goodfellas. Plus, as Don Leporeleone said Casino has more parts with DeNiro in it

Still Goodfellas is a fantastic movie, not a big fan of Ray Liota's character Henry Hill. Watch the movie Narc if you want to see Liota's best performance of his career. He was absolutey electrifying

"Running a casino is like robbing a bank with no cops around. For guys like me, Las Vegas washes away your sins. It's like a morality car wash" Ace Rosthein