I have flown on both on the ATL-MEX route. I don't imagine JFK-MEX is much different. The service and amenities were comparable on both.

I have only one caveat which probably applies to both airlines for the return trip, assuming meals are catered in MEX. Don't eat the salad. Although I had not had a problem on all of my previous trips, the last time we returned from Mexico (after my wife warned me not to) I again ate the salad on my meal tray. About an hour later (fortunately we had already landed), I became violently ill and remained so for the next six hours. Then I was fine again. I am sure that such an occurrence is pretty rare, but it was so unpleasant that I won't chance it again. The same advice holds in Mexico unless you are eating at a nicer restaurant which takes precautions to protect our sensitive tummies!