I've stayed at both multiple times. There is little difference in the rooms (small). As written above, staff at the Russell are very friendly and helpful. As an example, the concierge FedExed the necktie I'd left in my room after checkout to my home. Essex House is more formal, and one could say snooty. Depends on whether you want to be closer to the UWS or midtown. I've enjoyed them both and prefer either over the W's or Sheratons in NYC.