As far as I know, SAP HCM is one of the best modules SAP has to offer. The way it integrates with other modules is amazing. On the other hand, the SAP controls are considered the most powerful amongst the ERP systems. I believe HCM has a good future, especially when clubbed with the MBA degree you have. One suggestion, before getting into the certification, it will be better if you have the practical exposure to the HR processes (if you do not have already)> This will help you in mapping the real scenarios and situations in SAP.
I would browse the other SAP Certification questions. There are some good answers that may address your question.
Also the certification section on SearchSAP.com has good information that will help.