I am a platinum delta member and LOVE Delta. Having worked for another airline DELTA is worth every penny and every effort to fly. That being said, JFK is a disappointment. We were told bad information on a delayed flight going to DTW then when we went to the T4 sky club and tried to rebook and get our bags transferred the attendant at the desk was so slow I thought we were going to miss our next flight. The sky clubs are much too crowded to get the relaxation I pay for with my sky club membership. I get better service and a quieter table at a restaurant near the gate. The airport set up is bad but not as bad as LGA.
Flying on DL try to avoid JFK, you’ll have a better travel experience. That being said, I still fly Delta only, unless under duress.