Pros-You will experience vast variety of clients, you can sharpen your skills from Handling client directly, media relations, writing and of-course dossier making. I have realized there are no limitation to use your each n every working skills, which will definitely help you to evolve yourself in PR industry.
Cons - I noticed they were giving very low package as compare to market. Suddenly you will be overloaded with no. of clients, it's very difficult to manage quite long list of client individually.
Rest it's all depend on your ability, you can yourself make any firm big & successful than today. :)