I like to use minky or fleece for kids quilts. Those little stinkers like to put their little toesies through the fabric so I get something tough! For regular quilts I like to use a busy print to cover up my quilting mistakes! If you want to show off your quilting, use a plain muslin. I think it looks neat to look at the back of quilts that experienced quilters have made. I've seen some that are brave enough to use colored thread on a white muslin - looks gorgeous!
So, I think you should choose according to how the quilt will be used or quilted. In other words, it's your call.