It's nearly impossible to say what employers as a whole value. There is an incredible amount of variation between employers and between different people in the same organization. Plus, a great deal will depend on the specific job role, the specific class, and the relationship between the two.
Some employers and interviewers will completely discount any sort of MOOC certificate. Others may give you credit for demonstrating an interest in improving yourself-- I'd rather employ someone that's constantly evolving their skillset than someone that is comfortable where they are today. Whether that credit would be worth the time and money you'd invest in the course is something you'd need to determine for yourself and that you'd need to compare against alternatives like getting an industry certification. If an employer gives you credit for a MOOC certificate, a verified certificate is going to be more valuable than a free certificate it's just a question of how much more valuable.
Occasionally, you may find a case where having a series of related MOOC certificates is highly beneficial to a particular candidate applying for a particular position at a particular company because you're demonstrating familiarity with a set of skills that is rare and in demand. For the most part, though, they're likely to have at best a small impact on whether you get the job. Of course, the verified certificates are usually pretty inexpensive as well so you'd have to decide for yourself whether the small financial cost is worth the likely small benefit.