I think there's a fair bit of variation between the Coursera courses.

I'm currently taking their Machine Learning and Computer Vision courses. The ML course is quite like what you described for Udacity: there are a lot of short lecture videos with questions embedded in them, online quizzes and automatically graded programming assignments. It's a very engaging way to learn and I'm getting a lot out of it. The CV course, on the other hand, has so far just been videos of the professor talking & no supplementary material.

I suspect that Coursera provides the platform and leaves how the material is presented on it up to the professor. The ML course has been run once already, so they presumably have the benefit of experience; whereas it's the first time the CV course has been run so it's quite possible that they just haven't figured out how to take full advantage of the platform yet.