After reading this - I think you folks are missing the point.
Ignore difficulty of one airport vs. another via train or black car.
Ignore Jetblue & Virgin footprint in the market at JFK.
Ignore delays at one airport vs. another but I agree EWR is the worst of the three!
Pay Attention - there are only THREE major airlines for contract corporate business. If your company uses *A - you are going to whatever airport is in your contract or connecting. So the choice will be - direct from EWR requiring longer/expensive commute time OR connection via LGA which nets higher travel time & risk of misconnect via ORD, IAH or DEN.
If you have choices you will choose the program you are loyal to because your $$ spend is as important and miles collected.
Finally, Delta is also giving up slots at EWR (if this passes) so curious which routes are they abandoning which allows UA to dominate a route and skyrocket prices for those connecting via EWR from *A partners.
It is possible the slot exchange is more valuable vs. business at JFK in the long run.