In v2.08, it's better to use Air Strikes rather than Air Bomb, because any unit whose strength has been reduced to 50% will be weaker than if it lost the city defence bonus but remained at full health. Some special circumstances affect this dictum, however.
1. If the city has 100% defence bonus, Strikes and Bombs will have equal effectiveness.
2. If you have enough bombers to flatten the defences and knock the defenders down to 50%, it doesn't matter in what order you strike and bomb.
3. Strike cities or stacks with Bombers, not Fighters, because of the collateral damge they cause. But use Fighters against single units.
4. If one of the defenders is a Gunship, it will never be the primary target of a Strike until all other defenders are down to 50%. Fortunately, Gunships are affected by collateral damage.
Now, what will happen in BtS ? Will bombing damage still be calculated as a % of the original cultural defence, or will the (reduced) percentage be subtracted from that defence. thus changing the number of bombings according to the defence strength ? And so on, and so on. I suppose we must wait and see.