Question... Use the switch to update or function

I know this is not a means to ask questions so little full of context , but my disadvantage is to ask for the most viable way to use a switch. if I leave it in the update obcion charged if the first is true , for example : public int val=0;

 void Update(){
 
 switch(val){
 case 0:
 //sentence
 break;
 }
 
 }

or they are fuction:

 funtionForSwitch(int val){
 
 switch(val){
 case 0:
 //sentence
 break;
 }
 
 }

My idea is that when in the update, always load the first case and I think that if I put several objects with an identical script , would have confrictos between them, and if I use a fucion , I think it would have to adjdicarcela to a button or some conditional to be activated . could you tell me which is more practical . or if they have some kind of view. They are the thanks