I can only go by my experience, staying at EIU twice and WH once in the last 3 years. My kids are now 7 and 5.
In my experience, there were few or no people at the Emerald Island pool when we drove by (and we did use it on two occasions as well.) EI was an extremely quiet community.
Windsor Hills has much more of a resort feel, and the larger and more elaborate pool complex draws more people. More people use the elaborate playgrounds (another plus for kids there) as well. We saw many more people strolling and walking at WH than EI. Since we travel the same week every year, I don't think I can chalk it up to time of year.
I think you will do better at finding friends for your son at WH.
We had our own backyard pools at both EI and WH, but the slides, games, and activity around the pool area at WH drew us down there several times.
However, you would have to consider whether you will be hitting the parks hard all day, in which case the resort amenities will go unused no matter how elaborate.