Sarcasm. Hulu has ads while Netflix does not. For me the cost of an ad is far more than $2 a month price difference because I always need to be there when they watch something. Kids watch a lot of the same things over and over. With Netflix I can watch a movie with them the first time and then have a conversation about fiction, and the what the characters did, and if it was the right choice. Then when they watch it again I can ask about it without having to watch it with them. With Hulu I have to see it every time because I have to explain how the ad is attempting to manipulate their emotions to sell a product. Since the ads are constantly appearing, and different ones are being shown, I have to push my message about thinking about what we consume in the media that much harder to compensate for their increased presence.
If it was just me, or my spouse, it wouldn't be as big of a deal. The Disney deal is clearly interested in targeting children with advertising.
I left Hulu last year, but at the time they offered an ad-free version for a few dollars more a month - much better experience.