Hi ntengwall,
We've been to both the IB* Paraiso (2003) and the Tucan (2004) and we preferred the Tucan. Here's why:
1. The Tucan is in Playacar where the colour of the water is just breathtaking. It's picture postcard perfect. At the Paraiso the water is also very nice but not quite as beautiful as in Playacar.
2. The Playacar beach is nice soft sand everywhere. At the Paraiso there is an area around the pier which is rocky. Although this adds to the charm of the Paraiso resort it also means you really can't swim in that area.
3. The Tucan is much smaller than the Paraiso so there is less walking involved. We did not mind the walking at the Paraiso because the grounds are very nice but when we forgot something in our room we much preferred being a couple of minutes away at the Tucan.
4. At the Tucan you can sit and eat lunch at the beach/pool restaurant and have a beautiful view of the ocean. At the Paraiso the restaurants are removed from the beach.
5. The Tucan is close to Playa del Carmen. It's about a 5-minute cab ride or 30-minute walk. Also there is the Playacar mall 5 minutes away which is a nice alternative to shopping in town.
6. The staff at the Tucan was friendlier and more outgoing, although this can change with the staff turnaround.
7. The jungle setting in the middle of the resort is quite interesting. And the resident monkeys are a nice bonus.
8. We stayed in Bldg 11 and we had a view of the ocean from our balcony without paying the extra to get an oceanfront suite. At the Paraiso none of the rooms except the oceanfront suites have a view.
Pretty much everything else (rooms, buffets, a la cartes, bars, entertainment) was almost identical at the two resorts.
Probably the only thing where we thought the Paraiso was better was the pool. It is gigantic and there are three big swim-up bars. Even though the pool at the Tucan is nice, if you really like pools the Paraiso would be better even though you don't have a view of the ocean from the pool like you do at the Tucan. The swim-up bar at the Tucan is quite small and located in a small,separate adult-only pool. And since the Tucan swim-up bar pool is set in a sunken pit area it tends to not get much sun during certain times of the day.
If you are interested I have pictures of both resorts here:
http://www.pbase.com/pgammon
We had great vacations at both the Tucan and the Paraiso so I'm sure you'll have a wonderful time whichever resort you choose.
Hope this helps.