Why choose the Viper:

Small - harder target to hit.
Fast - able to get away from danger
Size - because pf it's size, it is harder to see it coming.
Cockpit - it provides better quality of vision.
TV Missile - The missile is pointed forward. Easy to align the missile.

Why choose the Havok:

Cannon - the cannon can obliterate enemy air assets.

Give me some more ideas...