Monster Zero x SciFi Japan - Archive Only

Legion's swarm was badly depleted by JGSDF ground fire.
AD autocannon put out a lot of projectiles, but they don't have that much ammunition, all things considered. They're designed to put controlled bursts ahead of and into individual aircraft.

By comparison to such bursts, gravity bolts are long-lasting and can be swept (to a degree) through a swarm. Factor in the monster's ability to fire continuously (autocannons' barrels heat up very quickly under the rates of fire they can attain) and it's easy to conclude that the swarm would fare much worse against Kaiser Ghidorah than against an AD unit.

Electromagnetic effects are "stronger" than gravity - at short range and low energy levels. Alter the individual numbers and the balance changes.
Consider Earth's gravity. Electromagnetic pulse can fry electronics across a wide radius, but electronics can be shielded fairly easily. Try making those electronic bundles rise against "weak" gravity. You'll have to constantly expend energy to do so, and the amount of energy required to lift the bundle completely out of Earth's gravity well is pretty damned high.

That's just a normal gravity well, too. Our present-day technology could, possibly, produce an electromagnetic weapon (probably a laser) with Momma Legion's firepower. (It wouldn't be portable, to say the least.)
As powerful as that weapon is, its beam is ever-so-slightly deflected by Earth's gravity.

Gravity can warp space itself if the gradient is steep enough. Hawking's quantum black holes may not actually exist, but they're theoretically sound the last I heard. A tiny mass, even by our Earthly standards, could still form a singularity if conditions were right. Since mass and energy are essentially the same, it's apparent that a gravity weapon does not have to have immense energy... though it may well have.

Gravity bolts - packets of force that have destructive tidal effect on matter -will give noticable deflection to an EM-based beam. (While I'm being pedantic, I'll point out that most kaiju beam attacks are EM, not just Legion's.)
Whether there will be enough deflection to spare Kaiser from a hit is a point for consideration, but if circumstances and timing are right it's quite possible... although an explosion is possible even if there is no stalemate.

I'm reluctant to go out on a limb and predict frequent singularity effects from gravity bolts, but the tidal interaction with high-energy particles - especially if all three gravity weapons are concentrated - is likely to produce a spray of even harder radiation. The same would occur if Legion's shield is used against gravity bolts, in which case the radiation spray will occur quite close to Legion.