Are arms or legs more important?

Neither are completely necessary for survival these days. If you had to choose to keep one set, I would keep the arms. If you don't have legs you can use a wheelchair so you are still mobile and not completely helpless. If you don't have arms you would need prosthetic arms, which are harder to come by than a wheelchair. You could even walk with your hands, or scoot along or something. It is very hard to write, eat, or pick things up with your feet.