Public vs Private w/get-set

Does anyone know if there's a performance difference or advantages between:

PHP Code:

---

public var somevariable:String 


---

and

PHP Code:

---

private var _somevariable:String
public function set somevariable(invalue:String):void{
   _somevariable = invalue;
}
public function get somevariable():String{
   return _somevariable;
} 


---

While I know that in cases where you want other commands, variable settings, statement, or certain subclassing - to run when getting or setting (say an event dispatch) - this can be valuable.
I'm trying to learn why it would be done the second way (with private) if there are no other commands,etc - just basically making a private variable with public function access.

The second way seems (to me) to be extraneous, but I'm hoping someone here can explain the wisdom and/or advantages of why it should be done the second way...

Thanks in advance.

-<>|TheMadFlasher|<>-

Personally, I think the get/set is 90% time overkill. Getters/setters are slower, code is be executed as opposed to accessing the value of a pointer. That being said, there are two strong arguments for using getters/setters and I do use them frequently. The first is that they can be defined in an interface, unlike vars and therefore makes casting to interfaces more powerful and enables "var like" access. The second is encapsulation, which I have mixed feelings about, were all your internal vars and methods are private and only the vars and methods you think are needed by the person using the class are exposed. In your example above you would do some validation on invalue before you actually set _somevariable.