We should prefer a monorail transit system to any other rail system for several reasons, among them that it costs a lot less to build. No property or rights of way need to be purchased.
Overhead rail can go anywhere without disturbing street travel and traffic can go between its pillars. Another advantage is that it eliminates the use of overhead cable and power poles along the route, an unnecessary obstruction.
Best of all is that overhead travel is scenic, comfortable and quiet.