Difference between passing: method that returns a widget, a unique widget class, or a Widget object - flutter

Question

I am confused between these three ways of passing/building widgets:
1.
Widget _myDisplay() {
return [widgets showing content];
}
#override
Widget build(BuildContext context) {
return _myDisplay();
}
#override
Widget build(BuildContext context) {
return MyDisplay();
}
where MyDisplay is defined as such (I'm not sure if it's crucial whether MyDisplay is a StatelessWidget or a StatefulWidget):
class MyDisplay extends StatelessWidget {
const MyDisplay({Key? key}) : super(key: key);
#override
Widget build(BuildContext context) {
return [widgets showing content];
}
}
Widget _myDisplay = [widgets showing content];
#override
Widget build(BuildContext context) {
return _myDisplay;
}
I've read this thread comparing the first two methods, and from what I understand, using a unique, named class extending StatelessWidget or StatefulWidget allows you to use the const keyword which signifies that it will not be rebuilt when the Widget tree is rebuilt.
However, what about the 3rd method above? Is it the same as 1. or 2., or completely different? If so, how is it different and when is it preferred?
Thanks!

Answer 1

Type 1: helper methods
Type 2: Widgets
Type 3: Variables
For type 1 and 2, I will highly recommend to check Widgets vs helper methods | Decoding Flutter
Helper methods will rebuild everything on every state changes which can be heavy based on scenario like using animated-widgets.
Try using Widget with const constructor to get better performance,
Now for the 3rd type variable. It is totally different from helper method and widgets. This variable won't change until you handle the variable state. Test this example code, and you will find the issue where data doesn't change on type3(variable) case.
class Test3 extends StatefulWidget {
const Test3({Key? key}) : super(key: key);
#override
State<Test3> createState() => _Test3State();
}
class _Test3State extends State<Test3> {
String data = "A";
late Widget _myDisplay = Text("$data");
Widget _myDisplayMethod() => Text("$data");
#override
Widget build(BuildContext context) {
return Scaffold(
floatingActionButton: FloatingActionButton(onPressed: () {
setState(() {
data = "b";
});
}),
body: Center(
child: Column(
children: [
_myDisplay, //variables doesn't update state(based on cases)
_myDisplayMethod(),
],
),
),
);
}
}