I'm not totally sure what you mean when you say Diploma Course other than you will receive a certificate authorizing you as an expert of sorts in whatever course it is you took.

Enrolling in any type of course that is geared toward the industry you wish to pursue will always make an impression. I don't know about giving you an advantage since some people may actually hold the degree requested and, even without experience, they are the ones with the most advantage. And your experience may even substitute for the degree, depending on the other employment criteria. 

If this course will provide you with credit toward an MA, that is even better because it will lead an employer to believe that you are serious about obtaining the degree.