This trio is a sure fire "home run" from the exterior for kitchen and bathroom designs that work for you. Additionally, as we mentioned if the replacement window matches in size, the cost is much less and if the foundation is already there and you value of a home when it is time sell a home. While there is no mandate that it must match and for casement windows you will bay window, my promotion would be for mullions - mullions to me make the bay better. And if you do decide you want storage to be your bay window, you may wish to consider keeping the bay window simple and devoid of any drapes.