in this code
```if( ! condition ){ if( ! another_condition ){ //do something } }
the second if( ! another_condition ) will be called only in the 1st condition was true.
In this code
```if(condition){
//return
}
if(another_condition){
//return
}
//do something
you will call 1st if and the 2nd regardless of the 1st one.
Just choose the case you need.