Welcome to the Disney Parks Mom Panel, Colleen!
That is a very tough decision. I think it comes down to the make-up of your group. If you have children I would suggest
Disney's Animal Kingdom. Animal Kingdom is easily toured in one day and features many attractions which children will love such as Kilimanjaro's Safari and the DinoLand U.S.A. area. Since it is easily toured in one day you will not feel rushed to cram everything in giving the children time to explore.
If you are traveling with adults I would definitely suggest visiting
Epcot. While there are plenty of things to do at Epcot for children, I find that adults are more likely to really dive into the experience of trying new cuisines and exploring cultures from around the world.
I hope this helps with your vacation planning. If you have any other questions please come back and see me.
Wishing you a magical Disney vacation and a pixie-dusted day!
Sue N., IN