User blog comment:Hayashi H/Spring 2016 Event Guide/@comment-26082413-20160507205807/@comment-26486243-20160508004115

Airstrike does a lot of weak hits - it will multiscratch boss, and is highly likely to kill all the PT Imp Packs outright, but it is extremely unlikely to destroy the artillery imps.

Shelling support does 4 strong hits (and 2 weak ones), which will likely deal less damage to the boss, but is more likely to taiha or destroy the Artillery Imps outright, while killing some, but not all, of the PT Imp Packs.

This is dependent on the equipment used by the fleet. If multi WG42s is a thing airstrike is better as it will focus the attacks on the artillery imps, making it more likely nothing except the boss survives to yasen. If one or zero WG42s are available it would be better to use shelling to increase the odds of destroying the Artillery Imps, as sinking PT Imps is no problem at all for a light fleet.