Which Riu really depends on what you might be looking for. We have stayed at all of them and so far our preference has been the Playacar.
The Yucatan we found to be primarily spanish and germans, very little english spoken, it is much larger than the Tequila and the Playacar but in terms of night life - pretty much non-existent after the nightly entertainment. The Playacar and the Tequila seem to have a better party atmosphere, and the pools were definitely more active than the Yucatan. And most definitely more Canadians and Americans at the Tequila and Playacar. The beach is identical whether you are at the Yucatan, Palace or Playacar, they are right beside each other (except there is a small resort between the Playacar and the Palace - Viva Maya I think.) The guest rooms are the same in each resort.
The food is the same, including the steak and seafood resturants. We found that out after eating at the steak resturant in the Playacar then booking the Yucatan only to have the identical menu. the we checked the Tequila and sure enough same menu.
Honestly though it's tough to tell you which one to stay at since you have run of the house at all three, so it really depends on which one you might want to hang out at the most and which one you want to spend your money on, the Yucatan being the most expensive (excluding the Palace) then the Playacar then the Tequila. Do remember if you are a beach person you might not like the Tequila since you are not on the beach and the resort is across the street from the beach. good luck in your selection and no matter which one you choose I'm you will like all of them since they are all equal in terms of what they offer.
