Here is my thinking on the purpose of the three you mentioned (which obviously can vary for many reasons) --
1. Mass Communications - in terms of business, this typically is an overarching area that includes internal communications, external communications and can even include PR. Generally focused on the company or organization's brand and communication tactics within the company (staff/employees) and outside the company (consumers/clients, competitors, general public). Focuses on communications campaigns via email, events and other digital tactics to disseminate important info and build brand image.
2. PR - will be very focused around generating a positive image, brand trust and brand awareness of the company/organization and is targeted solely at external stakeholders. This of course involves a lot of press release writing, but can also include events and social media -- any tactics to create a positive impression/experience/engagement with consumers/public.
3. Digital Communications - this can take a variety of forms and directions and I would say it includes things like: paid social campaigns, social media engagement, online web presence/phone presence, creating multi-media content using video/photo for web/phone/broadcast. Generally think in terms of creating digital content that can be used/shared to engage with whoever your stakeholders are and that can come in many forms -- video, blog, podcast, website, phone, social media, ect. Again, still focused on creating brand awareness and driving messaging and perception of a brand/company/organization.
So, obviously you can look at each major's coursework and compare them to see the differences and what interests you most. If you already have an idea of what sparks your interest most in terms of the type of work/career focus you may want to have then great! If not, I would suggest going with either mass comms or a PR degree. Both give you a great foundation in writing, crafting messaging and using social/events for engagement.
For reference, when I was in college I ended up getting my degree in PR, mainly because I was good at writing and it sounded interesting. I then ended up in event marketing for my first internship and job. I also then decided to get a Masters of Mass Communication - Integrated Marketing focus which gave me great insight and practice into integrating all kinds of communications and marketing and now I serve as a marketing manager for a consulting company. Either way, mass comms and PR will give you a good foundation in my opinion - and then you'll just see what opportunities come and where the road leads you! Good luck!
Devon recommends the following next steps:
- Compare the programs and courses required.
- Think about what sparks your interest the most.