fast.ai 1 is much better than Udacity's ML if you want to do purely Deep Learning. Udacity's DLF ND is IMO better than fast.ai 1. However, fast.ai 2 is way better than Udacity's DLF ND, and only their self-driving car has some Deep Learning models that are even more awesome (imagine driving using Deep Learning only). Take both fast.ai 1 and DLF ND if you are a beginner; after that jump on Stanford's CV & NLP courses; Oxford NLP might be a good idea as well. Then do UCL's Reinforcement Learning and you are set.