I am not a sap related professional but if you have scope of getting job then only you should do that certification. But sap jobs are available in mostly in MNC companies.So if you have experience only you will get jobs in such companies.
I am microsoft certified person so i am working in ERP and have experience also. I think if you do SAP certificaiton than its good to get nice job but certificaiton in Microsoft ERP also can help to get good job.