The airline with the best average rating is Delta Air Lines with 7.3/10.
The average flight time is 6 hours and 24 minutes.More information
This was my last UA flight out of JFK.
Almost booked this year's trip on AA out of JFK due to UA's move to EWR but then got a very nice MP promotion from UA so kept this year's trip with them. From my midtown office it's really not that much different in getting to EWR vs. JFK but I admit it certainly does have a physiological impact on me. To many in the city, EWR is so not NY and our airports are JFK and LGA. Not sure if I will keep my LA business with UA beyond this year - will find out in a month and report back!
Lastly, if you want to read a well balanced commentary on UA's exit from JFK, Mattew at upgrd has a very good article worth your 5 minutes of the day.