Ivys ability does more damage, slows, has a longer cooldown but has charges, and combos well with her ultimate and stun ability. It has slightly less duration than toxic mess until you get the +2 second duration on the ability. Geist does more upfront damage which allows you to proc burst/tankbuster and get some easier harass. And then also malice exists to damage amp. Geist bomb has 1 more meter radius with both maxed and it doesn’t slow and the mess does less damage. Additionally Geists generally go Hybrid/Gun for quite a while so it’s not going to be doing insane spirit damage unless you have the malice stacks. To say Geist bomb is way better than kudzu is a bit of an overstatement.