I'm going back for Summer Alumni 2011, but my first CP was Fall 2009. In that program, I lived at Vista, and I loved every second of it. Hopefully I'll get put there again in May!
All I can give you are generalizations and opinions about the complexes, but I think it'll give you a better idea of the differences.
Vista, during my CP, was the center of all social activity, mostly because it was also the main hub for transportation and the education center. The lifestyle at Vista is very open and friendly. You're really likely to meet someone who needs help carrying groceries, party with them that night, and become friends for life. All it takes to befriend someone there is to say hi, and it seems like everyone is always out walking around. That being said, Vista is the worst when it comes to living situation. The rooms are small, and the complex is something like 30 years old, just with a new paint job. I had to open my oven every time I needed to open the silverware drawer because of the kitchen design lol. But I didn't care one bit.
Chatham and Patterson are very nice compared to Vista. Spacious apartments, great pools and workout centers. Also, the rent is $20-30 more a week. There aren't so many people walking around all the time, so running into people and making friends isn't so common. From walking around Chatham and Patterson, it's much quieter and calmer than Vista.
So. Both complexes have parties, of course. Vista is loud, cheap, ****ty, nonstop busy. Chat and Pat are quiet, more expensive, new, and comparatively tranquil.