WPF-difference-between-deriving-from-ChildWindow-vs-Window

CODE:
<wwpf:ChildWindow x:Class="WealthLab.Custom.Extensions.PortfolioBuilderWindow"
        xmlns="<a href="http://schemas.microsoft.com/winfx/2006/xaml/presentation" target="_blank">http://schemas.microsoft.com/winfx/2006/xaml/presentation</a>"
        xmlns:x="<a href="http://schemas.microsoft.com/winfx/2006/xaml" target="_blank">http://schemas.microsoft.com/winfx/2006/xaml</a>"
        xmlns:d="<a href="http://schemas.microsoft.com/expression/blend/2008" target="_blank">http://schemas.microsoft.com/expression/blend/2008</a>"
        xmlns:mc="<a href="http://schemas.openxmlformats.org/markup-compatibility/2006" target="_blank">http://schemas.openxmlformats.org/markup-compatibility/2006</a>"
        xmlns:wwpf="clr-namespace:WealthLab.WPF;assembly=WealthLab.WPF"
        xmlns:local="clr-namespace:WealthLab.Custom.Extensions"
        mc:Ignorable="d">
    <DockPanel LastChildFill="True">
        <ToolBarTray DockPanel.Dock="Top">
            <ToolBar>
                <Button Content="Run"></Button>
            </ToolBar>
        </ToolBarTray>
        <Grid>
            <Grid.RowDefinitions>
                <RowDefinition Height="*"></RowDefinition>
                <RowDefinition Height="Auto"></RowDefinition>
                <RowDefinition Height="*"></RowDefinition>
            </Grid.RowDefinitions>
            <TabControl>
                <TabItem Header="Portfolio One"></TabItem>
            </TabControl>
        </Grid>
    </DockPanel>
</wwpf:ChildWindow>

CODE:
<Window x:Class="WealthLab.Custom.Extensions.PortfolioView"
        xmlns="<a href="http://schemas.microsoft.com/winfx/2006/xaml/presentation" target="_blank">http://schemas.microsoft.com/winfx/2006/xaml/presentation</a>"
        xmlns:x="<a href="http://schemas.microsoft.com/winfx/2006/xaml" target="_blank">http://schemas.microsoft.com/winfx/2006/xaml</a>"
        xmlns:d="<a href="http://schemas.microsoft.com/expression/blend/2008" target="_blank">http://schemas.microsoft.com/expression/blend/2008</a>"
        xmlns:mc="<a href="http://schemas.openxmlformats.org/markup-compatibility/2006" target="_blank">http://schemas.openxmlformats.org/markup-compatibility/2006</a>"
        xmlns:local="clr-namespace:WealthLab.Custom.Extensions"
        mc:Ignorable="d"
        Title="PortfolioView" Height="450" Width="800">
    <DockPanel LastChildFill="True">
        <ToolBarTray DockPanel.Dock="Top">
            <ToolBar>
                <Button Content="Run"></Button>
            </ToolBar>
        </ToolBarTray>
        <Grid>
            <Grid.RowDefinitions>
                <RowDefinition Height="*"></RowDefinition>
                <RowDefinition Height="Auto"></RowDefinition>
                <RowDefinition Height="*"></RowDefinition>
            </Grid.RowDefinitions>
            <TabControl>
                <TabItem Header="Portfolio One"></TabItem>
            </TabControl>
        </Grid>
    </DockPanel>
</Window>