Yes, it is true that for many of the quilt backs produced are of inferior quality. I have gotten a handful that seem to be of equal or close to equal quality of the regular size. I was going to purchase some grunge in the 108" size in hopes of it being similar, but according to one responder here, it apparently is different.

For backings I use mostly 108 fabric from MarshalslDryGoods.com, and sashing depending on what Im making. I was just checking out MDG and they had over a hundred and seventy Panels to work with, all kinds.

I like Marshall Dry Goods. I have purchased batting and fabrics from them and have always been satisfied.

My favorite white is Kona Snow, and I always buy it in a wide backing for every area of my quilt since it is cheaper by buying it that way. I also appreciate not having to piece strips as often since it is so long. I've never found it to be of a different quality from the 42" yardage. I buy it on Amazon.

My favorite place to buy other wide backing is Memory Lane Quilting. I like their price, quality, variety of patterns:
www.memorylanequilting.com
(330)468-2831