It's a big business competition, but I feel like the two theme parks are very different. To me, they have different draws. I far prefer the rides at WDW, as I am not one for scary thrill rides and big coasters. That said, Harry Potter at Universal is a big draw.
Absolutely not. Many folks work for both Disney and Universal. It is not unusual to find Disney and Universal teaming up to do things for local charities or when there is some type of disaster. They have a friendly competition. There are enough tourists to go around!