As a newbie in the realm of PR, it would be best to start out in a PR Firm.
In the book, Public Relations Strategies and Tactics  9th edition by Dennis L. Wilcox and Glen T. Cameron, there is a helpful selection where they compare PR Firm to Corporate PR.

Here are some of the things they stated (pg. 121):
PR Firm~
•    Fast-paced, exciting
•    Abilities get honed and polished
•    Networking with other professionals leads to better job opportunities
•    High emphasis on tactical skills, production of materials
•    Variety. Usually work on several clients and projects at the same time. Possibility of rapid advancement
•    Salary traditionally low at entry level

Hong Kong #108- this is it By: Thomas Birke

Corporate PR~
•    Jobs more difficult to find without experience; duties more narrowly focused
•    Sometimes little variety at entry level
•    Can be slower paced
•    Same “client” all the time. Advantage: Get to know organization really well. Disadvantage: can become boring.
•    Growth sometimes limited unless you are willing to switch employers
•    Salaries tend to be higher
There are pros and cons to both avenues.  At a PR firm the money would be so-so starting out compared to a corporate PR position.  Also, at a corporation I could focus on one thing that I felt strongly about promoting instead of many different things at once.

Nevertheless, I feel that as a college student fresh into the PR world, it would be easier to get my feet wet in a firm.  I think that I would be more apt to be hired at a PR Firm then a corporation because I would not have that field experience they desire.  I could gain that experience at a firm.

From an outside perspective I think that it would be beneficial to gain more contacts this way and be able to rise and increase more opportunities for myself.  At a firm I would be mentored and polished as a PR practitioner to be the best I could be.