Been in construction most of my life, the pink and blue are the same type of product. Same process, r value etc. They come in a variety of trade names but are all similar. Blue is a Dow product pink is an Owens Corning. The one that is readily available or cheaper would be the choice. Need to save weight go to 3/4 inch. You shouldn't be needing sideways strength just something to attach too. I assume your concern is dimples and stuff from humidity.