As a NYC resident myself, the points made above are all great and valid, so I won't dwell on them further.

But as you do mention international vacations and miles, if you're interested in using miles to fly premium cabin international long-haul, you should keep in mind that an equivalent amount of UA/AA miles will get you much further than with DL in that specific use case (and you will earn them at same rate with each airline at a multiple of your ticket price). The downside is you will have to endure their comparatively less impressive operational reliability and service consistency for your regular travels.