I used to be the Manager Of the Mennonite Quilt Center in Reedley, CA. The batting that we used at the center to tie the comforters was polyester 12oz. Since we were a store and a quilting center we were able to buy it on wholesale. And we were also the drop off point for oversea shipping of the West Coast Mennonite Central Committee, so many were with 6oz. Sometimes church organizations would asked us to add and order for them when we placed our store order....then they would get a 25% discount.
6oz is pretty thin so I guess that 5oz is thinner and that would work well in the LA, I have used the 6oz several times when customers have brought it with their quilts. There is not too much loft with it.
I am not familiar with Marshalls batting..so my response refers to Hobbs and Quilter's Dream.