This example shows how, in a majority of cases, Streams cause unnecessary rebuilds in initial state.

stream_vs_valuelistenable.dart

import 'package:flutter/material.dart';
import 'package:rxdart/rxdart.dart';

// Global application configuration and navigation

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) => MaterialApp(home: Home());
}

class Home extends StatelessWidget {

  Widget _button(BuildContext context, String title, WidgetBuilder builder) => RaisedButton(
            child: Text(title),
            onPressed: () => Navigator.push(
                context, MaterialPageRoute(builder: builder)));

  @override
  Widget build(BuildContext context) {
    return Column(
      mainAxisAlignment: MainAxisAlignment.center,
      children: <Widget>[
        _button(context, "Streams", (c) => StreamExample()),
        _button(context, "Notifiers", (c) => NotifierExample()),
      ],
    );
  }
}

// Basic view that displays two properties

class ExampleView extends StatelessWidget {
  final String title;
  final String description;

  ExampleView({@required String title, @required String description}) : this.title = title ?? "<EMPTY>", this.description = description ?? "<EMPTY>";

  @override
  Widget build(BuildContext context) {
    print("ExampleView built with title:'$title' and description: '$description'");
    return Scaffold(
      appBar: AppBar(title: Text(this.title)),
      body: Text(this.description),
    );
  }
}

// With Streams/RX 
// ----
//
// Two initial rebuilds while we know we have values.
//
// I/flutter (31663): ExampleView built with title:'<EMPTY>' and description: '<EMPTY>'
// I/flutter (31663): ExampleView built with title:'Stream's example' and description: 'This shows how Streams with empty inital data cause more rebuild than ValueListenable.'
  
class StreamModel {
  final title = BehaviorSubject.seeded("Stream's example");

  final description = BehaviorSubject.seeded(
      "This shows how Streams with empty inital data cause more rebuild than ValueListenable.");

  Future<void> dispose() async {
    Future.wait([
      this.title.close(),
      this.description.close(),
    ]);
  }
}

class StreamExample extends StatefulWidget {
  @override
  _StreamExampleState createState() => _StreamExampleState();
}

class _StreamExampleState extends State<StreamExample> {
  final model = StreamModel();

  @override
  void dispose() {
    super.dispose();
    model.dispose();
  }

  @override
  Widget build(BuildContext context) {
    return StreamBuilder(
        stream: model.title,
        builder: (context, title) {
          return StreamBuilder(
              stream: model.description,
              builder: (context, description) {
                return ExampleView(
                    title: title.data, description: description.data);
              });
        });
  }
}


// With Notifiers/ValueListenable
// ----
//
// Only one build since ValueListenable always has a stored value.
//
// I/flutter (31663): ExampleView built with title:'Notifier's example' and description: 'This shows how Streams with empty inital data cause more rebuild than ValueListenable.'

class NotifierModel {
  final title = ValueNotifier("Notifier's example");

  final description = ValueNotifier(
      "This shows how Streams with empty inital data cause more rebuild than ValueListenable.");

  void dispose() async {
    this.title.dispose();
    this.description.dispose();
  }
}

class NotifierExample extends StatefulWidget {
  @override
  _NotifierExampleState createState() => _NotifierExampleState();
}

class _NotifierExampleState extends State<NotifierExample> {
  final model = NotifierModel();

  @override
  void dispose() {
    super.dispose();
    model.dispose();
  }

  @override
  Widget build(BuildContext context) {
    return ValueListenableBuilder(
        valueListenable: model.title,
        builder: (context, title, _) {
          return ValueListenableBuilder(
              valueListenable: model.description,
              builder: (context, description, _) {
                return ExampleView(
                    title: title, description: description);
              });
        });
  }
}