An out of area Realtor can learn a new neighborhood, but must be willing to invest the time and energy necessary to acquire the knowledge.
In an ideal situation, you will have local representative for a Realtor who knows the market, is well connected with affiliated businesses to call in as necessary, be well respected by other agents in the area, and have first hand knowledge of buyer preferences for that area.
If I had to compromise and couldn't "have it all" in one package, I would give consideration to a Realtor who was from a nearby neighborhood who had excellent skills, and was deeply committed to me as a client. I give great weight to the value the Realtor brings to the transaction, and the right Realtor can venture outside of their immediate area and be very effective.
I have seen buyers have their Aunt Mable from 80 miles away help them through a transaction because they felt obligated and so Aunt Mable could get the commission. If Aunt Mable isn't going to driving the buyers to see all the properties with you, internalize the market data, tresearch whatever is needed, and maintain a hands-on approach, then pass on Aunt Mable.
As a sellers agent, the priority is on the merit of the offer and the likelihood of closing. A strong offer that does not close is worthless. If there is reason to suspect the contract may not make it to closing, I will share those reasons or suspicions with the seller. A buyer agent can build confidence or cast doubt on the liklihood of closing.
Bottom line....Choose a knowledgeable and committed buyer agent, preferably from the immediate neighborhood you seek to buy. If you have a great agent from a nearby area, he/she may be well worth it. Companies all across America place a high value of talent.
Best of luck with your home purchase.