And I would recommend the first option. In EK F, there is really no 'late' departure (and the consequent reduction in service/experience) - what those of us in the US would consider 'late' isn't at all what people in the ME would consider so. I'd most definitely take the 10:30 pm departure from JFK and enjoy drinks, a nice dinner, perhaps a movie, and some good sleep time prior to landing at DXB. A 4-hour layover is VASTLY different from a 13-hour one, especially at DXB. Thirteen hours in simply not enough time to go into town and have any sort of experience except trying to get in all the sights, while at the same time watching one's watch! Do your first option!!!!