Personally, when I'm interviewing and reviewing resumes, I mostly look for the curiosity and drive to learn on your own. So while a more official certificate certainly carries more weight, don't underestimate what it means listing Coursera courses and experience kaggling on your resume.
Also from my experience, just sitting down on the weekend and working through some popular methods and tools to have the very most basic knowledge is appreciated a lot - again curiosity and a drive to learn more is the most important thing.
So while a certificate will definitely carry weight, most interview processes include their own way of validating your data science chops. So I think the distance in renown between doing nothing and doing some free classes is much larger than the one between free classes and more extensive courses/certificates.
But a very important distinction is hands-on experience. If these certificates or boot camps (e.g. Zipfian Academy) give you the opportunity to work on actual projects, possibly even for some clients, that would be the added-value to look for! Being able to talk in depth about an as-realistic as possible data science project is a great advantage!