if you are going just to do the rides in the parks, 3 days would work.
going just for the rides/shows, it can be done.
stay where you think it is the best deal for you.
when someone asks about the crowd calendars and wonders if ep's are needed, i assume that the trip is for rides and shows basically.
i'm sure you could complete the parks for everything in a 3 day time.
when i go, i stay onsite as i make it a total relaxing vacation.
i'm not there just for rides in the parks but the entire universal property.