If my rack is ugly, then the roof rack is F
The point is to have a sturdy, reliable rack with minimal affect on the car, its performance, and its appearance.
Trunk-mount rack - scrapes up paint over time; least sturdy option
Roof-mount rack - seriously affects the aerodynamics of the vehicle; exposes bike to the elements (sandblasting effect and moths); exposes roof to dings from falling bike; exposes bike and roof of car to disaster if you pull in the garage (requiring extra precautions)
Hitch-mount rack -- the hitch is barely visible (the least visible of the three). When the rack is connected, it doesn't touch the paint and is extremely sturdy. It also goes on and comes off extremely fast - faster, even, than the trunk-mount. Clearly the winner here.
Friday night - rack goes on, bike goes on, ready to roll out in the morning (club ride starts at 7:30). At club meeting point, bike comes off, no need to remove wheels. After ride, come home, and rack comes off in mere seconds.