It’s better to have your camera point toward a solid background, away from windows. The problem with cameras that can see through glass is that they might pick up plants moving around on a blustery
day, or passing vehicles even. Again, if you want
to detect motion at a first floor window, then place the camera to one side, not opposite it. This will eliminate two problems at once. The first is that it avoids detecting irrelevant motion. The second is that it catches the intruder as they walk “across” the camera’s field of view rather than into it.