The short answer is, none.
When you use the analogRead function, “0” and “A0” refer to the same pin, the analog pin 0.
So, when you use analogRead, it doesn’t matter which pin designator you use.
But, if you want to use the analog pin 0 with digitalWrite then you must use “A0”. If you use just “0” then by default the digitalWrite function will use digital pin 0 instead.