I guess I am just the opposite. I enjoyed Oahu much more than Cancun. The beach and water in Cancun are much better, but I don't like the hotel zone. You don't get any real feel for being in Mexico. I think that Puerto Vallerta is much better for this.
In Oahu, I like being in the middle of things. You can then take a bus or a rental car and be in a quiet little spot in no time.