Ask yourself what kind of sewing you will do.
If you are a quilter, the 15-91 or 201 do FMQ and piece great.
If you do garments or home dec projects or the like, the 401 has the stitches you need. What I don't like about the 401 is that the bobbin is horizontal and the needle plate rises to disengage the feet. Neither of those work for me in quilting. I do own one- I got it cheap at a garage sale and use it for zig zag or blind hem.
You cannot beat the straight stitch machine for perfect straight stitiching. I have a 201 and a 15-91. The 201 is an elegant machine, but I use the 15-91 for sewing bindings on as I sew the whole binding on by machine.
I have to say, my machine of choice for piecing and FMQ is the 301, which I love the best.