https://www.youtube.com/watch?v=SiO 9Ph01YlM Skip to 8:31. W

The moral difference between cutting off 1 or 2 or 5 mens heads and dropping a bomb on a hospital full of kids?

Well the hospital full of kids are incapable of defending themselves, making the crime more morally degenerate.
Also the method of execution. Cutting off someones head is personal (so it contributes to the destruction of moral repulsiveness in the executor) and also likely to take longer.
Bombing someone is, albeit, slightly less repulsive, as a method since it is more likely to kill rapidly, and it does not destroy as much of the fabric of the mind of the executioner.

however bombing is also likely to produce collateral damage and injured persons so:

In the balance of things I would say bombing is worse, as long as bombing is intentional and specifically directed at children.

Also the question would need to be asked why are they cutting off peoples heads.

So intention becomes 9/10ths of the law in this case.