Look at the commonalities between the 3 careers – PR, Advertising and Journalism. All the three require creative storytelling ability. Of these Advertising is the most challenging because of time and money constraints.
Having said that, PR is very closely related to Journalism. In PR you are a Corporate Journalist working for the company. Job is the same but a different role.
But in terms of variety, traditional Journalism is better but probably pays lesser. Among the 3, Advertising takes the cake in terms of variety and creativity but its a very difficult career to get into.
I hope you find this information helpful, see you on the next topic.