It all depends on what it is you are ordering from Marshall. Some fabrics I've seen at Hancock's. Some (a few) are name brand quilt fabrics, but older lines. I would say that the wide backings they have are not the quality of your local quilt store, but more than likely more along the lines of Hancocks or Joann quality.

BackSide Fabrics - Your Best Source for Wide Quilt Backing Fabric | has a large assortment of backing fabric and has some name brand lines as well. I think their backings are probably better quality.