The travel time is probably close to 2 hours from LI on pub transit vs less than a half hour from Jersey. Im sure that the PATH train is walking distance from the Jersey CG ,then 15-20 train ride to downtown NYC. From LI, its Lido Beach?, theres the undetermined trip to LIRR , a change in Jamaca Queens to a Penn Station train. More involved trip, more time. I live on Long Island now, and if going to NYC for a show or whatever , drive instead of training it. After the 11pm train, its hours between trains from Penn Station outbound. This only works because I have parking options not available to most.
Moral, my vote ,Jersey CG.