Tomahawk, it can roughly do everything the Dragonfly can plus more.

FANG, because of nostalgia and you could have a squadron (which I did...over time). It was a early workhorse of Cobra.

The Mamba was bigger, more expensive, took up more space. Also, i'm cool with the futuristic concept, but I felt the Mamba needed two things, a bigger cockpit and landing gear. It had great firepower and one of Cobra's best pilots, though.

Additional comments on other copters:

Swampfire: rotor blade assembly was too fragile. Also, lightly armed.

X-Wing Copter: Hate the phallic machine guns. Needs landing gear, too. Vehicle seems cramped...to fit in price point, I guess.

FANG 2: Not actually copter, but whatever. I liked back when, but doesn't do much for me now.

Locust: Decent Joe minicopter, if unrealistic.

Retaliator: Needed bigger rotors and sturdier skids...too much weight on those skids. The crane thing seems absurd, but you can ignore it and use it as a heavy lifter copter.

Dominator: Fails as a tank and a copter. Where's the tail rotor? I've tried to like it, but just seems lacking.

Battle Copters: They are just gimmicks...never used them much.

Razor Blade: Decent colors, ugly design due to string racer gimmick.

FANG 3: One of the worst vehicles ever.

NAC: Has a tonka feel to it. Weird rotor design. Not bad.

Missile Storm: One of the worst vehicles ever.

Crimson Command Copter: Got one...never actually opened it. Maybe someday.