I have to agree with all the posts!
Aruba is heaven, paradise as compared to the other islands. A few of the islands I've been to on cruise ship stop overs you can't even relax on the beach without vendors coming up to you trying to sell you stuff. In Cancun the minute you try to exit the airport, men dressed in tan troussers and blue shirts come up to you asking for your passport just to get your attention. They pretend they are custom agents or something and then try to sell you timeshare.
The beaches in Cancun are very beautiful like Aruba. From the plane it is such a lovely view. However, at the resorts I find a lot of beaches are not swimmable. A lot of rocks, strong waves, rip tides etc. A few of the resorts I stayed at in Cancun had the beach separated by flags. Red flag meant too dangerous to swim because of rip tides, waves and rocks, yellow proceed with caution and green safe to swim.
In Aruba I go to Eagle Beach and when I enter the water I'm in there a minimum of 1 hour sometimes up to 2 hours. Just swimming, floating on my back without a care in the world..