If using 16" on center grid joists I always used inexpensive plain 1/2" CD sheathing plywood with the best side up. The best side usually has plugs and knot fillers in it. Over the years I have always had either Homasote, Ouietbrace or various thickness of extruded foam covering the plywood---more recently foam as shown in my little attic senior citizen layout[2010 photo].