One possible thesis statement for a comparison essay of the style of "Miss Brill" and "The Yellow Wallpaper" could be that the social expectations that are placed upon women do not gear toward their empowerment, but toward the continuation of their sub-serving nature- always serving, always nurturing, and always providing a service while getting none in return.
When we look at the character of Miss Brill, herself, we find a woman who has lived a life of righteousness and prudishness, as she is expected to live. As a middle-aged, single woman, society has limited her tremendously to follow a specific role. In return, she gets the limited joy of a walk in the park and the humiliation of not being able to expand her femininity as she should be able to do.
Similarly, the main character of "The Yellow Wallpaper," is another woman who is trapped by social expectations: A woman with a tremendous trauma is misunderstood by her husband, and all of those around her, simply because she is not following the rules of society bestowed upon mothers. She is not the bouncy, happy, nurturing new mother society expects. Instead, she is a victim of a severe post partum depression and becomes trapped in a room (instead of liberated) as her only choice to solve her problem.
Therefore, the thesis statement that societal expectations may hinder women from achieving their fullest potential, is because they are obligated to abide by a series of rules that may be counter-productive to them.