Interesting, every person we have ever shown how to sew with a handcrank has said that it was WAY easier to control and be more accurate....
What folks do not take into account when considering this, is that there is a direct "connection" between the action of your right hand and the action of the feed dogs pulling the fabric through. It is as though you are pulling it but it is "virtual"
With an electric motor, you lose the feeling of control over the feed and to the second hand is needed for stability. With a handcrank, you hold/guide the fabric in line with where you want the seam and you "pull the fabric" through with the feed dogs.
Once a person has done piece work on a handcrank, they almost always say that going back to electric is hard to get the same control.
My .02