I like Coursera over Udacity in terms of the way that their courses are presented. Long videos are better than short ones, and Udacity's frequent quizzes mean I can't watch lectures while (say) chopping vegetables or doing some other mindless task which gets my hands dirty.

However, the content is what really matters. I definitely like (so far) Udacity's Self-driving Car course, and I can also recommend Coursera's Machine Learning. They do cover a tiny bit of the same material, but they do it so differently that it's worth taking both. Definitely skip Coursera's Computer Vision course.