Public Relations - Master or CIPR Diploma?

I'm thinking about doing additional study to diversify my skills. I have a BA in Film and Media Studies and have worked in media for two decades.

I'm thinking of moving into PR but don't want to have to start further down the ladder. I'd like to be able to step into a mangars or senior position with my experience. To bolster my profile I want to gain additional qualifications.

My question is what is more worthwhile? What would make me more employable? An MA in Public Relations and Corporate Comms or Charted Institute Public Relations Diploma?

Any insight would be much appreciated!

Thanks