Dear Sir or Madam:
A wise man once told me that all good questions get answers that start with these two words: "That depends..." In your case, where you wish to choose between more post-grad education versus certification depends on your answers to these counter-questions:
1. What do you want to do in the field?
2. How soon do you wish (or need) to start generating income?
3. What are your long-term goals?
In general if you want to work as a technical specialist of some kind, if that work doesn't involve research or development, certification is usually a workable approach. Also, given that earning a Master's usually takes at least a year (and sometimes two), it might be that a need to earn a paycheck sooner or later would dictate a cert rather than another degree (though the cost factor can also lean those on tight budgets to certs rather than degrees as well).
But the long-term goals thing inclines me to observe that certs vs. education may be a false dilemma, in the sense that there's really no reason why you can't do both, especially if you can plan for a longer time horizon. In fact, it's very often the case that people who earn certs to advance their careers discover research and development interests that lead them back to school, onto Master's and even Doctoral level advanced degrees. Perhaps this might even happen to you.
Hope this helps. If you have any followup questions please post again,