Maybe the difference shouldn't be whether its city or not. I been to both places and I can tell you that I didn't enjoy the HOT weather in Cancun. Its a place where you have to run into a store to get some relief, while Hawaii has the famous trade winds. If you like balmy weather then Cancun is for you. Don't be fool into thinking all tropical places are the same. It may look the same in pictures, but there is a reason that Mexican has siesta time. They are overwhelm by the weather and sleep during that time. People in Cancun will do this in the afternoon. Hawaii does not have siesta time.