[Lokibob]

Cheaper, more powerful, and do a different job. Bombs are used against a fixed target, like a building. The hellfire missile is designed to kill a tank even if it is moving.

[SauronOfMordor]

Bombs are used against a fixed target, like a building. The hellfire missile is designed to kill a tank even if it is moving.

"Smart" bombs can be steered into their target. When you're dropping at terminal velocity, a small turn of the steering vanes can produce a very respectable lateral movement -- more than enough to stay on-target with a moving tank.