I haven't been to Dreams but I have been to Moon Palace. Here are some thoughts...
-It's a really, really big resort. It's actually like 3-4 resorts sort of put into one. I can't remember what the name of the section we stayed in was, but it's the section with the animal buildings. I don't remember the room number, but it was the second floor of the building with the red bird sitting on a green twig. Helpful? Haha! Anyway, we had a great view of the Catholic wedding gazebo and watched several weddings from our balcony. I love how they bring brides up in the horse drawn carriages. Anyway, my biggest complaint was the size. It took forever to walk anywhere and you had to wait forever for a shuttle. My friend was 24 weeks pregnant when we went and it rained almost the whole time we were there (mid-April). The tiles they use for the outdoor walkways get EXTREMELY slippery when wet (I doubt they were made to be outdoor tiles!) so we would walk everywhere using the covered walkways so it took us at least 7-10 minutes to get anywhere on our side of the resort.
-The rooms are AMAZING! I think we booked the lowest level resort view room, but we could still see part of the ocean from our room. The beds were beyond comfortable! My pregnant friend didn't want to leave because she actually slept well at night in them. The hot tubs in each room are amazing even though it's a *little* odd that they are in the middle of the rooms. We only used it one night but it was nice.
-The food is fantastic. We would always go to a restaurant for "first dinner" and then a few hours later order room service for "second dinner" (pregnant friend, remember?). I enjoyed every meal, although the room service quality and timing went downhill later in the week as the resort filled up more and since it was raining I think more people were ordering. Still good though.
-Free calls to the US and free internet (in 2010 anyway) are a huge, huge bonus! I was able to call clients and do some work online while I was there without spending any extra money.
-GREAT pools! But during our stay the beach was closed so we couldn't enjoy that. The rain brought up a bunch of muck and they didn't clear the sea weed off the beach the whole time we were there which was a little disappointing. Even if we could go in the ocean I still would have liked to lounge on the beach, but they didn't even put the chairs out. The pools made up for it, but it wasn't the "beach" trip I was expecting.
But even the bads (a little too big and it rained almost the whole time) didn't spoil all of the amazing goods for us. And I really, really like how they do weddings. If you want to be treated like a princess I recommend getting married here!