I would think it this way:
"For the most part MOOC certificates don't mean too much in real life. It is whether you can actually solve problem matters. So the meaning of MOOC is really there to stimulate you to learn. And certificate serves as a motivation tool.
As for OP's question. I never take the Udacity nanodegree. From what I heard though, I will say the nanodegree will require effort to take 1 to 2 Ng's deeplearning.ai specialization. It's also tougher if you need to take a course in a specified period of time. But the upside is there are human graders which give you feedbacks.
As for which path to go, I think it's solely depend on your finance. Let's push to an extreme: e.g. If you purely think of credential and opportunities May be an actual PhD/Master degree will give you the most, but then the downside is it can cost you multi-year of salaries. One tier down would be online ML degree from Georgia tech, but it will still cost you up to $5k. Then there is taking cs231n or cs224d from Stanford online, again that will cost you $4k/class. So that's why you would consider to take MOOC. And as I said which price tag you choose depends on how motivate you are and how much feedbacks you want to get."