I would recommend a white on white, in fact you may want to get several and inter-mix them since the rest of the quilt is scrappy. I say this because when I was making a Double Irish chain, I was using a pansy fabric with green on the outside edge. I kept putting it together and used 3 different greens until I finally settled. (Can't tell you how many of the blocks I took apart.) Then when I was finally done, was getting it ready to hand quilt when I saw someone using the white on white and that was it. I set a square of her fabric on top of the white fabric in the quilt and i just popped. I was SO tempted to take the full sized quilt apart but I haven't. It is still waiting for the quilting to be finalized. (That was about 8 years ago.)
So if nothing else, I suggest you audition the 2 before making a decision.