What are the benefits of having buyer representation?

[Michael Martorella]

I've begun looking for my first investment property and have read in multiple posts that you ought to have a real estate broker/agent dedicated to you (as the buyer) instead of using the listing agent (seller's agent). I'm wondering how many of you abide by this rule and, if you do, what are the benefits? I understand the concept of fiduciary duty and a dual agent, but I'm not understanding how a buyer's representative would benefit by pushing for a lower purchase price (and thus lower commission).

Assuming one does want to interview and 'hire' a real estate broker, should they be local to the target city or is it enough if they're familiar with the general region?