No, I really think windows are not so much an architectural element but a functional one from the inside of the house.
Nonetheless, if exterior symmetry is of importance to you, there may be some ways to fool the eye. For instance, if one window is not as long as another, a window box can be created below the shorter window to create the illusion of length. If two windows share the same sill height but one is not as tall as the other, a small awning can trick the eye into believing the windows are the same size (if the awning is also over the higher window).
I just made the choice to keep one window on the side of my house as is, and shorter the other. Because this is on the first floor, I landscaped under the shorter window to disguise it is not as long as the other window in the next room.
I say do what you want because it is your house and you need to make it comfortable for yourself.