But can't the katty and stuka do the same?
Katyusha yes, although you need to protect it more since it fires 4 times.
The stuka zu fuβ is different, since there’s no difference if you fire it from min or max range and you fire on a straight line so your targeting is different.
All 3 are good in my opinion, though I am a fan of the stuka zu fuβ.