I'd also base my decision off of what airport you find yourself flying out of frequently. If you live in Jersey and find yourself frequently flying out of Newark I would not consider Delta since you'll have to connect 90% of the time. On the other hand a lot of people like using Delta out of LGA, since they have a lot of routes to non-hub cities as well as very frequent service to DL Hubs and 2 Skyclubs.

When I was in NYC I preferred Jet Blue, since my office was right next to Penn Station and it was easy to get to their JFK hub with the LIRR + Airtrain. They also had the best fares and the best equipment (IFE on every seat).