Real estate agents do their research in regards to comparable properties in order to come up with an asking price, and you may get different responses from different agents. Once someone makes an offer, unless it's cash, the lending bank will require an appraisal, and that's the number that matters, as the bank won't lend more than what the house is determined to be worth.
As an agent, I looked at comps to come up with prices, but I always found that the appraisers came up with properties I would not have considered and made adjustments for features in a way in which I had no expertise. I would say talk to at least three agents and pay attention to the person with whom you feel you can work. I understand the advice to get someone with lots of experience, but I will point out that some successful agents won't have time for you and some new agents will devote all their time to you. And as a former agent, I will say that how quickly a house moves has as much or more to do with the market than to the efforts of the agent.