A bit off topic, but there may be more to it than the "best deal". During your search, you'll get the best service and not have to answer the same question a hundred times and work around several agents' schedules to see properties if you select just one agent to help you locate properties, determine their market value, arrange showings, and then finally negotiate and present contracts and manage the transaction to closing.
You really need to make the decision *before* you find the home, so if you include the above in your decision making it seems clear to me that having one person to help you is better for you. There should be nothing preventing that agent from getting you a great deal. And if you do that up front, you'll be able to interview several agents and choose the one that can best represent you and understand your needs.
(Many buyers make this decision half-way through the process, after they have called a few agents and are getting tired of the mortgage qualification questions...so they usually wind up with the next listing agent they call. Since agents aren't all the same, you may not get the best one for you...)
I can match buyers anywhere in the world with a good, experienced buyer's agent through my network -- as can many other agents.