We've stayed a VdM and looked at the rooms at the B. This is sort of an apples and orange comparison.
VdM- Can be noisy from traffic on Melgar until 11 PM or so. The balconies are nice as long as you turn off the AC so the heat doesn't blow on you. The rooms are very clean and the bathrooms are very small. The plus is that you can walk to everywhere. The pool overlooks a vendor area and is very small. The people there were very nice. No elevator if that is an issue.
The B has great snorkeling a really hip/cool patio and pool area. The food is good, but the service can be spotty. It's a $5 cab ride to town, so that is cheap. The rooms are smallish, but they have balconies overlooking the water. As they face west, these are the ones you want for the sunsets.