I can pretty much guarantee that whatever park you are at, will be the busiest. And then if you leave to go to another park, that park will then become the busiest. Unless I happen to be at the parks the same time, and then the park I am at, and the ride I am in line for will be the busiest.
For the most part, unless you are talking about a 3-5 point swing, you won't be able to tell the difference. And that Epcot can handle an extra 5-10,000 people much better than DHS can.
Remember, that simply by telling people a particular park won't be crowded, you increase the crowd at that park and decrease it at others. If no one had told you a given park should have been less crowded, would it still have seemed less crowded when you are there? To quote Yogi Berra "Nobody goes there anymore, it's too crowded.".