Set, get, send and message passing syntax

Design
1

Assuming we are within the scope of a specific component, controller, or route that looks like something like this:

App.ThingController/Component/Route = Ember.Controller/Component/Route.extend({

     myString: "string value",
     myFunc: function(){
       // do something and return value or object
     },
     saveFunc: function(value){
       // save value somewhere
     },

});

What is the difference between the following syntaxes:

var someValue = this.myString;
var someValue = this.get('myString');

var someResult = this.myFunc();
var someResult = this.send('myFunc');

var anotherValue = "foo";
this.saveFunc(anotherValue);
this.send('saveFunc', anotherValue);

this.set('myString', anotherValue);

In other words, specifically what do I lose by not using the getters and setters or the send method? What specifically is gained by using them?

Are there any important cases where I absolutely must use the send or a setter/getter syntax? Perhaps some observer/binding behavior?