I decide whether I want the colored pieces to stand out or whether I want the background to blend in with them. For a modern quilt with strong color and spare pieces I use a solid white. For a quilt where I want the feeling to be more traditional, I use a white on white muslin with perhaps little flowers or stars.

I love the look of the white on white prints. On my Mini Pinwheels quilt (picture posted sometime back) I used a several different white on white fabrics for the background, but the borders were done in one fabric.

white on white
 

I guess I usually use white on white, but I use the "wrong side". It gives just enough interest to keep me happy and doesn't show the ridges or blobs that look as though they could be picked off.
Just sayin'
Purl

I have done both & I like both but the white on white is my favorite of the two.

I like Kona Snow or the Moda Bella equivalent, or light gray. The other background I like is a batik neutral tone on tone print rather than the white on whites to give a bit of depth to the quilt. It really depends on the tone of the fabrics I'm using and I can't say I've made a lot of scrappy quilts yet.

I use both. Some patterns I feel look better with white and others with white on white. If I am piecing blocks I use white on white but if I am using it as a background for applique I like solid white.

I just bought 8 yards of the grunge white on white. I also mix my different whites to get more dimension in a quilt. Choose what works for you.

I use plain white al the time or snow.

I prefer a Kona "Snow". Love it and can always find it at Hobby Lobby where they will still honor the 40 percent discount here.

I like white on white, in assorted leftovers, for scrappier look!