Given its pure role as a heavy bomber, the Kirov's only real shortcoming is its inarguable lack of speed--a problem that is partly resolved by the Kirov's posh living quarters and spectacular panoramic viewports, which let their prestigious pilot-bombardiers blissfully pass the time while their aircraft steadily trudge along toward their unfortunate targets. Along the way, Kirovs are able to simply shrug off most anti-aircraft fire, including attacks from enemy fighters. It is true, though, that Kirovs have no means of retaliating against enemy aircraft, so the Union does tend to send escort fighters of her own to watch over each mighty vessel, just in case. Further, Krasna Aerospace has equipped this year's Kirov models with special fuel injectors that provide the airship with a significant burst of speed, though this is used sparingly for safety reasons.
The vehicle we know as the prospector is basically just a well-put-together material supply truck suitable for the collection and transportation of raw resources. Even if it does convert into a military command hub, the prospector is close cousins with civilian trucks, and like most civilian trucks, carries no defenses whatsoever. Because of this unassuming nature, the Allies continue to express concern and dismay that prospectors now appear to be priority targets for Soviet forces. It wasn't always this way. Originally designed as industrial pick-ups, prospectors gradually became more important to Allied field posts and strategic holds. Soon enough, these vehicles began to see action on the front, in the midst of conflict with Soviet forces.
You can read the full articles, along with short videos of these units in action here and here, at RedAlert3.com.
