I mean I would think the majority of players would just end up going for both. One of the main points of playing a dating sim is that you get the option to see what it's like to be with all of the available girls. But if you're saying if the users had to pick one then I'm sure there would be people who would pick the "less attractive character" over the other character. You mentioned that both characters are just as equally developed, but characters can be just as developed while at the same time have completely different personalities. This difference in personality can easily be the difference in picking one girl over the other. Even the difference in attractiveness is subjective, and varies from person to person. When I was playing through Katawa Shoujo(a dating sim) there was a character named Hanako a girl with a burn mark on half of her face, this could be described as a "physical imperfection", yet I found her attractive, and she was the first girl I picked.