Flash onData vs. onLoad

Hmm,
I think I forgot to answer your question.

You should use onLoad method when you're expecting name-value pairs of data, because they will be automatically converted to properties so you can comfortably use them. Example:
---
data.txt:
name=John&age=35&city=New York
---
var myLoadVars = new LoadVars();
myLoadVars.onLoad = function (success)
{
    if(success)
    {
        //here you have access to all data converted to properties of myLoadVars object
        //so myLoadVars has from now on "name", "age" and "city" prop. and you can use their
        //values:
        trace(this.name);
        trace(this.age);
        trace(this.city);
    }
}
myLoadVars.load("data.txt");
-----

You should use onData method when you're expecting other than name-value pairs encoded data, for example some raw text, article ...  Example:
---
data.txt:
This is great article about ActionScript. It's great. Blah blah...
---
var myLoadVars = new LoadVars();
myLoadVars.onData = function (src:String)
{
    //src parameter contains loaded data
   trace(src); // this will trace out: "This is great article about ActionScript. It's great. Blah blah..."
   // so you can assign it as is to some TextField
   _root.article_TextField.text = src;
}
myLoadVars.load("data.txt");
-----

I hope it's clear now.

Regards,
ivan_os

ivan,

Thank you very much for your concise and accurate explanation! I have used both methods many times before, but never really figured out why! go figure...Anyway, I do understand better now and gladly award you all the points. Thanks again!