While the Iberostar Costa Dorada is a beautiful resort, the Riu complex is just a beautiful, a bit more remote and out of the way from POP but, you get the use of all the Riu resorts with their package, so I would take advantage of being able to use more facilities at the Merengue, Bachata and Mambo.
Here is their website have a look
http://www.riu.com/index.php
Have a look through their website.