They do more damage and there's even an upgrade in the campaign which makes them decent at dealing with a bunch of units. --- You don't understand because there is nothing to understand. It's nonsense. -Bahamut
Banshees are anti-ground units and are /good/ at it.
Vikings are anti-air units and are /good/ at it.
Wraiths are an odd mashup of both and aren't especially good at either. --- https://www.youtube.com/watch?v=sJaO5J4R7vw If I say something, it is liable to be misinformed or otherwise incorrect. You have been warned.