Three lovely choices! I have all three but use my 401 the most. That's only for the decorative stitches, I am a quilter and do my piecing on a 301. I would choose the 401 basically because they don't show up as often and when they do people ask a lot for them. It could depend on where you live but in this area I can find 15-91's easy peasy and pretty cheap generally. I've heard some people say 201's are rare in their local areas but I've found a few around here so it wouldn't be my first choice.
No matter what you decide you win. These are all wonderful machines.