Granny is quite different to her other weapon options. While the other two are better for short-mid range, Granny excels on medium-long range. As Quanrian affirms, it plays differently (remember: sidegrades, nor upgrades). Instead of spraying short burst over your target, you want to aim more precisely -headshots are important! With Granny, Mikah won’t become a sniper, but more like a platoon designated marksman.
Recoil can be difficult to handle, but you get less dispersion to keep the pressure on distant targets -something more complicated to achieve with the other weapons. It also helps that Granny has a larger magazine -the largest in the game, if you exclude Konstantin’s chain fed Gatling or Kuzmann’s ray gun. But bear in mind each magazine has a different recoil!
It is also a great option for damaging unmoving or slow objectives, like the Beholder or the Protector’s shield, if playing as the Antagonist.