Iberostar. My personal recommendation would be the Paraiso Lindo. There are two "campuses" (if you will) in Playa del Carmen. One, North of town, has the Del Mar, Beach, Lindo and Maya (lower end to upper end respectively). We stayed at the Del Mar and it was very lovely. The rooms were very nice and clean, but we preferred the grounds and the clientele of the Lindo. The Lindo and Maya guests can use the facilities at the Beach/Del Mar, but not vice-versa. I would highly recommend any of these four resorts, but if we ever go back, we'll stay at the Lindo.
Now, I would also consider the Iberostar Tucan or Quetzal which are in a gated community on the south side of Playa del Carmen. If you want to be closer to town, this would be a better choice.