Good question. It does make a difference.
One problem with hatching the first eggs a pullet lays is that many pullets do not lay perfect eggs to start with. It can take a while for a pullet to get the flaws out of her internal egg-making factory. You are probably familiar with obvious flaws like thin-shelled or no shelled, extremely thick hard shells, no yolk, double yolk, no whites, and just weird shaped eggs. There can be other issues with how the egg is put together you would never see just by looking. If the egg is not pretty much perfect it won't hatch with a healthy chick. A surprising number of pullets get all this right to start with but you can't count on it.
Another problem is that the first eggs a pullet lays are generally small. They don't hold enough nutrients or have the room for the chicks to grow to a decent size. I've hatched some of these small eggs. Many of them that actually hatch do fine but I've noticed the hatch rate is not as good as if I wait to set them and that more chicks die before they get to two weeks of age. I almost never lose a chick that hatches but when I do it is often a chick from a small egg.
One hatch I noticed that the eggs from a young pullet was not fertilized. I set 5 eggs from one young pullet and none hatched. I set 6 eggs from a different young pullet and all hatched. My conclusion was that she had not yet learned to allow the rooster to mate her or he did not know she needed to be mated.
These problems seem to pretty much go away after the pullet has been laying for at least a month. The glitches in forming the egg have generally been worked out, the eggs are a bigger, and she has socially matured enough that the eggs are fertile. I've had good luck if I wait at least a month.
Good luck!
