poly also comes in a low loft. it doesn't have to be overwhelmingly puffy. even the low loft is fluffier than w & n.
does he like a heavier weight or a lighter weight? that's a difference, too.
machine stitching through a high loft poly can be hard. it's very easy to get puckers if you don't baste it or pin it a LOT. will you be LAing or domestic machining?