Everything. They have absolutely nothing in common.
You can unscrew a light bulb!
One can't see to go the other can't go to sea.
One shoots but can't hit, the other hoots but can't sh...
He works it out with a pencil.
Absolutely nothing
A Specialist knows more and more about less and less until he knows absolutely everything about nothing. A Generalist knows less and less about more and more until he knows absolutely nothing about everything.
One shoots and shoots but can't hit, and the other...