The 'to watch or not watch the ball' discussion is missing the point.
The real point is you can not afford to keep your head down.....defined by.....still looking at the tee or point of contact after the ball has been hit. The desire to control the head like that greatly inhibits the body's ability to swing in the high level pattern.
Watch what two of the highest level do.
http://hittingillustrated.com/library/AGonzalez14.gif http://hittingillustrated.com/library/Pujols11.gif
Keeping your head down....to look at the tee or point of contact? Why.
You've lost sight of the ball several fractions earlier.
Do not limit what the body needs to do by 'overly fixing' the head.