Amtrak fares were higher, and the train was slower, at least from New York.
(Although the bus passengers could go to other casinos, apparently in practice they tended to stay at the one the bus went to.) So at the time casinos were providing buses from your neighborhood to a casino for fares like $10, and providing chips and other freebies in addition. As I recall, the casinos liked buses better because a bus went to one casino, while train passengers could go to several.
As far as I can tell, the Amtrak Atlantic City venture failed because the casinos didn't provide train passengers with as much free stuff as they did bus passengers, and the transportation from the Amtrak station to the casinos was poorly done.
