WPF control in VSTO add-in - ElementHost vs. native WPF Window?

I have a VSTO Microsoft Word add-in. When the user clicks a ribbon button, I want a WPF window to show up. I had always thought the only way to do this was by adding an ElementHost control into a Winforms form and adding WPF controls on top. But I discovered via here that I can also do the same thing by converting a WPF UserControl into a WPF Window and using control.Show() to display it. This seems to obviate the need for using ElementHost. Before I go down this path, any reason I shouldn't do this? Is there any technical difference or speed difference in doing it this way?