These stealth bombers can only be revealed by radars in close proximity. Each bomber takes some 200 energy per second to keep stealthed so using alot of them requires some serious infrastructure.
Each individual bomber does about 3.3 times as much damage as ordinary bombers and if you can avoid radars they can destroy targets deep within enemy lines.
They can bomb without revealing themselves.
They can surprise an unsuspecting player but some radars and fighters will quickly dispatch of these fragile and expensive bombers as they lack any AA-capability.
Godde: Personally I think the risk is too high.