Okay, so when you're mixing dough by hand versus when you're mixing it by machine the two yield basically different results. A machine has a powerful motor, and so in a professional kitchen the motor is so powerful, that what that motor does is it beats air into the dough and it oxidizes the dough, and therefore it causes the fermentation to occur more quickly.
When you're kneading something by hand, you're really not adding the same kind and ditto for when you're using a stand mixer at home. You're really not adding a lot of air, like a professional mixer would be adding into your dough and so you have basically, a slower fermentation process which generally yields more flavor.
That's one of the reasons why I'm a fan of mixing dough's by hand, because you're not adding that air. You're not accelerating the fermentation process. You're slowing it down and when you're slowing it down you're just adding more flavor to the dough. Those are some of the main differences between mixing a dough by hand and mixing a dough by machine.