Air attacks.

[Imp]

Most of the level bombers do pack a good wallop if they actually hit where you intended they do often jump a hex row or 2 which can be alarming. As someone said before cost wise they are not the best choice but if your using for atmosphere as in say an airmobile force so no arty available till landed or at best a bit of support by the big guns with a long reach they can do the job.
The biggest diffrence between air & arty really is arty is far more predictable air is always the bigger gamble it can pay huge dividends or be a total disaster. As said cost wise arty nearly always comes out on top as has more shots & the ability to keep firing at a targeted location.
Level bombers are probably the worst of the lot as really just one shot arty that has a good chance of missing its target, they should always be used pre plotted as think this does improve the accuracy & they do have very high call times.