An academician knows what he/she can do and what he cannot. An administrator thinks he/she can do everything
An academician knows and realises that he knows a few things about a few things. An administrator feels he knows everything about everything
An academic beleives he can learn from others. An administrator feel he can always teach others
An academic beleives in taking everybody along. An administrator feels he can always ignore others and bulldoze his own ideas.
An academic displays contentment. An administrator os always discontent because of overambition.
An academic is always ready to accept his mistakes while an administrator always tries to find reasons to rationalise them.
Those who can they do
Those who can't they teach
Those who can't teach they administrate (or manage)
Some more are available here