Which is better for a 4 year old - Epcot or Disney's Hollywood Studios?

We are going back to Disney in a couple of days... We have 2 days left on our 4 day p. We are definitely doing Magic Kingdom. We've already done Animal Kingdom. Which of the remaining parks are best for a 4 year old? Epcot or Hollywood Studios? He's an active 4 year old, who enjoys rides.