From Supreme Commander Wiki
Strategic bombers are one of the units that can easily turn the tide of a battle. They are fast and powerful, making them great for taking down commanders. The key to using them is to know their strengths. And all four factions have different ways to use them.
[edit] Factional Differences
UEF Ambassador: The Ambassador features a small yield nuclear bomb. It has the most HP and has an AA gun mounted on its back. Making it usable without air support, therefore more efficient. Great for starting players learning the UEF. Following the UEF's combat strategy of heavy armor, the Ambassador is resilient against up to the toughest air defense grids.
Cybran Revenant: The Revenant holds true to Cybran style with its adaptability and low HP. It is the lightest but has a stealth system and an AA gun for self-defense. It does less damage but has a rather large explosion radius. Great for taking out swarms of units.
Aeon Shocker: The Shocker drops a smart bomb that can adjust its course slightly. This allows it to easily hit smaller targets. It is also the most powerful of the bombers, but has no splash damage. It also comes with decoy flares.
Seraphim Sinntha: The Sinntha is exactly between the Ambassador and the Shocker. It has no AA but is quite powerful when attacking single targets. It is rather resilient so don't expect low end AA to even really scratch its painting job.