I have talked about this before (but apparently a few New Yorkers disagrees with me here), but bare in mind I have lived in NYC, Northern NJ, Mid-Jersey, Philadelphia, and now I live in Eastern Pennsylvania (yes, I love to move.)

But here goes, most people living outside of NYC hates going to JFK because it is always a risk of traffic jam going to JFK. Also, JFK to Manhattan is not an easy commute either. Going Belt Parkway up BQE to the bridges is guarantee traffic. Going up Grand Central Pkwy to LIE west is also traffic nightmare most of the day.

EWR on the other hand is a great place to fly. It is easy to get to from Eastern Pennsylvania, Philadelphia, South- Mid- and North- Jersey. Also, landing in EWR is only 30-40 minutes to Manhattan depending on tunnel traffic. You can go up GW Bridge, Lincoln Tunnel, Holland Tunnel, etc.

I know for a fact most people living outside of NYC in Jersey, Philly, Pennsylvania, etc. would absolutely not go to JFK. My peers think I'm crazy going to JFK just to fly CX.