I am facinated with how design and layout effect the feel of a living space...
We decided we did not want the entrance to our master beadroom to be at the end of a long, dark hallway, but diretly off our living room. We saw this design on a number of newer floor plans. The window to the right in the picture was already in place (four feet wide), so we made the french doors the same size.
This design choice has symmetry to it, giving the door balance against the window.
When we put the window in the end of our master bedroom, we made it the same size as the doorway, so there would be a framing effect. I think a wider window would off-balance. Finally, both windows give a nice view outside, working together to bring the outdoor feeling inside.
Here is a picture of the window next to the larger window on the adjacent wall.
All of this comes together to give a great view and comfortable feeling.