Perhaps surprisingly, there are several important benefits to you, the seller, in choosing an agent conversant with lenders, loans, and current rates. Doesn't matter how wonderful the sale price is if the buyer can't perform. Among the most important are:
1) Having an agent who can quickly determine the buyer's ability to qualify can save much gnashing of teeth later. Buyers rarely come in pre-qualified in the sense that you probably think of it. Don't be lulled by a "pre-qual letter"; a) most of them have so many caveats as to make them close to worthless, and b) the source of the letter is at least as important as the content;
2) The most common contingency in real estate contracts is the buyer's ability to obtain financing. This contingency is structured such that, if the buyer is unable to obtain a loan equal to or better than certain criteria, he can get out of the deal, leaving you with no recourse. Having an agent who knows what current rates are (they vary depending upon the size of the loan and the loan-to-value ratio) gives you the ability to rid the contract of a common (and huge if it arises at the end of the escrow) issue;
3) Having an agent knowledgable about loans can actually result in a higher sale price for you. Huh? A couple of years ago I had a house in RHE listed for $950,000. The sellers had interviewed several other agents, none of whom recommended an asking price over $899,000. My approach (looking at it 100% from my client's perspective as I always do) was "look, we don't have to sell the house tomorrow -- let's put it out at $950,000 and see what we get. We may not get $950,000, but we certainly won't if we don't ask it". About 2 weeks later we got an offer from a buyer wanting to do a lease-option, which is rarely in the seller's interest. The buyer actually wanted to buy, but he only had 10% down and most people will tell you that a 90% loan in that price range is just not going to happen. He had made several offers on other properties, all rejected, and was frustrated. I knew of an obscure lender that, based upon the buyer's credit rating, would probably make him the loan. That is what happened, with a sale price of $945,000.
This crucial area of the business is often poorly understood and rarely discussed, but in this and other cases, I have been able to get a higher price for my sellers simply because I keep abreast of lenders rates and terms.