Hm, i would use it anytime really, its good for any scenarios. If you use it as your first move, they will probably hold on to their stomachs and kneel down like they were throwing up in the illusions while they are in pain. While theyre distracted i would use the stone spikes to come up from under them and dropping lid to come up on top of them, killing them >:3
Advantage: A genjutsu that actually costs damage, which is rare nowadays and it can be used for distraction as well.
Disadvantages: 3 handseals and the enemy is still able to perform handseals :T_T: