It depends on the quilt's design and the look you're after. I have white solids ranging from bright snow white to antique white to very off-white, as well as white on white prints that offer a little pattern and texture when you want a little bit more interest without being distracting. It's good to have this type of variety in your stash so you can experiment and learn what appeals to you and what doesn't.
Try not to overthink this; embrace the choices we're offered from the fabric manufacturers and play away!