The question is confusing as noted above, UA does not fly JFK-MEX. The OP appears to be trying to seek UA 737-800 vs UA 787-8 experiences and then apply it to travel on Aeromexico.
Given the general nature of the question and that it has been cross-posted here, I am going to close this thread and direct responses to the original one:
http://www.flyertalk.com/forum/other...o-jfk-mex.html
Thank you,
FlyinHawaiian, Co-Moderator
United MileagePlus Forum