I can only speak for the Tequila as I haven't been to the other I'm sorry. We loved the Tequila and it had the added advantage that you could use the facilities of the other 2 Riu hotels that are really close. I think I'd feel a bit confined if I were to go AI to just one hotel. Maybe this could swing it for you if the prices are similar.

Just returned today from Riu Tequilla, no problems at all, apart from not having access to the sea, all beds moved, sand is being pumped from the sea bed to make the beach wider, stop it being washed away. We were not informed of this by Thomson before we travelled. 3 days no beach. JCB,s Diggers, Big pipes, mounds of sand, not a pretty sight. Spoilt our last three days.

we were at the gran bahia principe,in oct & would definately return.
it is made up,of 3 sections.the coba,tulum & akumal.you have use of all 3 & you get around,by hopping on,the little tram like buggies,that run from 7a.m till 3a.m.
the hotel & grounds are spotless.
i don't think you will be disappointed,
tracy

I also went to Gran bahi principe in July. It was magnificent. Loads of restaurants. Totally spotless, gorgeous beaches and food. Me and my now wife got engaged on the beach in front of the caribbean sunrise. It was stunning. Only fault is that it is a bit far from the towns, such as playacar or rivieria maya. They are definitely worth a trip out. In truth though we would have been quite happy to stay in the hotel complex the whole time.

Many thanks for all the replies, I must say they both sound great and it's dificult to choose between them.

Shame no one's been to both, but I think I'm leaning towards the Bahia Principe as it seems just a notch up from the Riu, quality wise. Only real downside appears to be the out of town location and a longer airport transfer.

costs about $3 in a collectivo,into playa del carmen.there is often one,waiting outside the bahia,on the main road,if not,just flag one down,as they pass be frequently.
tracy

I've been to the Tequila, but not both. Tequila has a great position being only 15 minutes walk or a $5 taxi ride to the town centre. I can thoroughly recommend it. It also has the advantage of being able to use several other Riu hotels as well (Yucatan, Playacar and Lupita) all in Playacar.
You need to determine what is important to you on holiday and then compare the features and location of each hotel and try and make a decision on that.