Why do you like Insta-cast or No Insta-Cast?

if you feel comfortable enough with the character and their abilities quick casting can make your actions alot smoother. there isnt much difference between having to click twice over once but split second decision making in the right hands with those few precious seconds can change the course of a fight. Say a Vayne gets jumped, knows what they need to do, and only need to click 5 times instead of 10 to get off a ult combo pin and click them until they are dead. those 5 seconds you spend trying to place something slower could be the same time someone needs to out play you. and if you are not as comfortable, normal casting is a more reassuring way of making sure things land.

Quickcast is quicker, which can be important. If you do it with indicators, instead of without, it even lets you use high-precision abilities accurately and quickly.