If proximity to the parks is your biggest concern, then the World Center property will win out. It is about as close to the Disney parks as one can get without being "on property". Though the Marriott Village properties aren't all that far away, but they are farther than the World Center.

But as you (and others here) have mentioned, there may be other influences as well.

When I travel down with my parents, siblings and their families, they like the Springhill Suites due to the extra space and free breakfast. I'm probably just weird, but I like the World Center property better myself. I usually get upgraded to a park view room. We usually get a very nice view of the evening fireworks show from the room. Or I will stay in one of the 3 World Center MVCI properties on the World Center campus.

I've also stayed at the Grand Vista property and it might be a good choice as well. It is newer than the MVCI "Palm" properties in the World Center and it has some very nice on-site pools and other amenties for kids and families. But to me, the older "Palm" units just feel more spacious and open (note they don't have the "lock-out room design" of the Grand Vista.)