Thank you for all your responses! I'm glad to know that I am not the only one who experiences this.
I have noticed the "competition" in the neckline area too, as some pointed out. I am trying to actually grow my hair a little longer than it is currently, because I am wondering if once I get it clearly past my shoulders, there won't be so much going on at the collar area. I also feel like hair that is exactly at shoulder length kind of creates a blocky appearance because it emphasizes the shoulders, if that makes any sense.
Aida, I find it fascinating that you consider your hair as one of the first things to consider when putting together an outfit. I usually leave my hair for last, because I like to get dressed before I do my hair, and if my hair refuses to cooperate for the day, I will put it up. But then the outfit might look different proportion-wise. Maybe I need to decide what I'm going to do with my hair first and then try to get dressed. Have you noticed any formulas that work better for you with your hair up vs. down? For instance, do you find you need to optically shorten your torso if you wear your hair down?
Suz, I have the same thing going on, a low bust and a long neck. When I wore my hair short, I had trouble with bigger, deeper necklines. With my hair longer, this isn't as much as a problem. And I am sad that my beloved turtlenecks just don't work very well anymore. I may try to find a very light-colored one this fall/winter, because my hair is dark and my skin pale, so maybe that will look better on me than a dark one.