Okay---I went to the Knoxville show last year and it was wonderful!!! I would highly recommend it. The quilts were fabulous and the vendor mall was great! There are also several nice quilts shops in Knoxville and the surrounding area.
Atlanta in October will be a Quilting Expo (as opposed to a quilt show). I attended it last year. It is much smaller than Knoxville and Paducah, there are not a lot of quilts and lots of the vendors were selling sewing and long arm machines.
If my choice was between Knoxville, Paducah and Atlanta---I would eliminate Atlanta and choose between the other two.