I've stayed at the Del Mar and the Lindo so I can't really comment on the Maya. But here are some things I can tell you. In order of cheapest to most expensive:
Grand In terms of access, it goes the opposite:
Grand (access to all)
Maya (access to Lindo, Del Mar/Beach)
Lindo (access to Del Mar/Beach
Del Mar/Beach (only access to each other) Pools:
Del Mar/Beach share a LARGE pool
Lindo/Maya share many separate pools.
I personally like the pools at the Del Mar/Beach because it's all connected. You don't have to get out of your pool to go to the swim up bar, 'just swim' =) At the lindo/maya, you get up and out to go the 'main' pool with the (1) swim up bar. Del Mar/Beach have 3 Restaurants:
We liked the Japanese at the Del Mar the BEST, and the gourmet is delicious!
And we also liked the Cajun at the Lindo. BUT you can go to the Japanese (and any Del Mar rest.) if you are at the Lindo/Maya because you have access to those resorts. Rooms:
I honestly couldn't tell you the difference in size (specifically) between the Del Mar and Lindo, but there was a difference, rather small. The Lindo had an extra door in between the bathroom, closet and refrigerator/coffee machine area connecting to the main room. But both had the kind size bed and couch, chair and coffee table before the balcony.
I did see hammocks on the balcony's at the Maya, that's pretty cool =)
Tripadvisor.com is GREAT. Lots of pictures and current reviews.